<PAGE>   1
                                                                   EXHIBIT 99.1


                                    MICHCON
                      INVESTMENT AND STOCK OWNERSHIP PLAN
           (As Amended and Restated Effective as of January 1, 1989)
<PAGE>   2


                                    MICHCON
                      INVESTMENT AND STOCK OWNERSHIP PLAN
           (As Amended and Restated Effective as of January 1, 1989)

                               TABLE OF CONTENTS

<TABLE>
    <S>               <C>                                                         <C>
                      Article I.  The Plan                                        
                      --------------------                                        
                                                                                  
    1.1               Establishment and Amendment of the Plan                      1
    1.2               Applicability of the Plan                                    1
    1.3               Purpose and Type of Plan                                     2
                                                                                  
                      Article II.  Definitions                                    
                      ------------------------                                    
                                                                                  
    2.1               Definitions                                                  3
    2.2               Construction                                                14
                                                                                  
                      Article III.  Participation and Service                     
                      ---------------------------------------                     
                                                                                  
    3.1               Eligibility Requirements                                    15
    3.2               Eligibility Upon Merger or Reemployment                     15
    3.3               Collective Bargaining Agency                                16
    3.4               Applications                                                16
    3.5               Years of Service                                            17
    3.6               Break in Service Year                                       18
    3.7               Hours of Employment                                         19
    3.8               Employment by Related Entities                              21
    3.9               Leased Employees                                            21
                                                                                  
                      Article IV.  Contributions                                  
                      --------------------------                                  
                                                                                  
    4.1               Employee Allotments                                         23
    4.2               Employer Investment Plan Contributions                      26
    4.3               Employer ESOP Contributions                                 28
    4.4               Additional Employer Contributions                           30
    4.5               Rollover Contributions                                      30
    4.6               Transfers from the MichCon Savings and                      
                        Stock Ownership Plan                                      33
    4.7               Transfers from the MichCon Employee Stock                   
                        Ownership Plan                                            34
    4.8               Limitations on Salary Reduction Allotments                  35
    4.9               Distribution of Excess Deferrals                            38
    4.10              Distribution or Recharacterization of Excess                
                        Contributions                                             39
    4.11              Statutory (Code Section 415) Limitations on                 
                        Allocations to Accounts                                   41
                                                                                  
                      Article V.  Vesting in Accounts                             
                      -------------------------------                             
                                                                                  
    5.1               Employee Salary Reduction Accounts, Employee                
                        Post-1986 Voluntary Deduction Account, and                
                        Employee Pre-1987 Voluntary Deduction Account             46
</TABLE>


                                     -i-


 
<PAGE>   3


                                    MICHCON
                      INVESTMENT AND STOCK OWNERSHIP PLAN
           (As Amended and Restated Effective as of January 1, 1989)

                               TABLE OF CONTENTS
                                  (Continued)

<TABLE>
    <S>               <C>                                                         <C>
    5.2               Employer Salary Reduction Account,                          
                        Employer Voluntary Deduction Account,                     
                        and ESOP Account                                          46
                                                                                  
                      Article VI.  Investment Provisions                          
                      ----------------------------------                          
                                                                                  
    6.1               Investment of Contributions and Allotments                  47
    6.2               Change of Investment Direction                              47
    6.3               Transfers Between Investment Funds                          48
                                                                                  
                      Article VII.  Investment Funds                              
                      ------------------------------                              
                                                                                  
    7.1               Investment Funds                                            49
    7.2               Management of Investment Funds                              50
    7.3               Voting of MCN Stock                                         50
    7.4               Tender Offers                                               51
    7.5               Named Fiduciary Status                                      53
    7.6               Expenses of Funds                                           53
    7.7               Primark Corporation Stock                                   53
                                                                                  
                      Article VIII.  Accounts and Records of the Plan             
                      -----------------------------------------------             
                                                                                  
    8.1               Company to Maintain Accounts                                54
    8.2               Plan Accounting                                             54
    8.3               Valuation of Funds                                          55
    8.4               Valuation of Investment Plan Account                        55
    8.5               Valuation of ESOP Account                                   55
    8.6               Valuation of Plan Account                                   55
    8.7               Company to Furnish Annual Statements of                     
                        Value of Plan Accounts                                    56
    8.8               Trust Agreement                                             56
                                                                                  
                      Article IX.  Distributions, Withdrawals, and Loans          
                      --------------------------------------------------          
                                                                                  
    9.1               Distribution Upon Termination of Employment                 
                        Entitling Participant to Value of Plan                    
                        Account                                                   57
    9.2               Distribution Upon Termination of Employment                 
                        Under Circumstances Resulting in Forfeiture               
                        of Employer Contributions                                 57
    9.3               Certain Distributions from Participant Accounts             58
    9.4               In-Service Withdrawals--General                             60
    9.5               Withdrawal of Voluntary Deduction Allotments                60
</TABLE>



                                     -ii-

 
<PAGE>   4


                                    MICHCON
                      INVESTMENT AND STOCK OWNERSHIP PLAN
           (As Amended and Restated Effective as of January 1, 1989)

                               TABLE OF CONTENTS
                                  (Continued)

<TABLE>
   <S>                <C>                                                         <C>
    9.6               Hardship Withdrawal of Salary Reduction                     
                        Allotments                                                61
    9.7               Time of Distributions                                       63
    9.8               Distributions of Stock                                      67
    9.9               Distributions from Fixed Income Fund                        68
    9.10              Loans                                                       71
    9.11              Definition of Allotments and Employer                       
                        Contributions                                             75
    9.12              Spousal Consent to Payment                                  75
    9.13              Distributions Pursuant to a Qualified                       
                        Domestic Relations Order                                  75
    9.14              Direct Rollovers of Eligible Distributions                  76
                                                                                  
                      Article X.  Administration                                  
                      --------------------------                                  
                                                                                  
   10.1               Plan Administration and Interpretation                      79
   10.2               Notice to Employees                                         80
   10.3               Notices to Employers                                        80
   10.4               Participants' Acceptance of the Provisions                  
                        of the Plan                                               80
   10.5               Audit of Plan Records                                       81
   10.6               Claims Procedure                                            81
   10.7               Effect of a Mistake                                         82
                                                                                  
                      Article XI.  Amendment and Termination                      
                      --------------------------------------                      
                                                                                  
   11.1               Amendment                                                   83
   11.2               Withdrawal                                                  83
   11.3               Termination                                                 83
   11.4               Allocation of Funds Between Employers                       84
   11.5               Trust to be Applied Exclusively for                         
                        Participants and Their Beneficiaries                      84
                                                                                  
                      Article XII.  Participation by Affiliated Companies         
                      ---------------------------------------------------         
                                                                                  
   12.1               Adoption of the Plan                                        86
   12.2               Withdrawal from the Plan                                    86
   12.3               Company as Agent for Employers                              86
</TABLE>



                                    -iii-

 
<PAGE>   5


                                    MICHCON
                      INVESTMENT AND STOCK OWNERSHIP PLAN
           (As Amended and Restated Effective as of January 1, 1989)

                               TABLE OF CONTENTS
                                  (Continued)

<TABLE>
   <S>                <C>                                                         <C>
                      Article XIII.  Special Provisions Relating to the ESOP      
                      ------------------------------------------------------      
                                                                                  
   13.1               Establishment of ESOP                                       87
   13.2               ESOP Account                                                87
   13.3               Discrimination Testing                                      87
   13.4               Loans                                                       88
   13.5               Diversification                                             91
   13.6               Put Option                                                  91
   13.7               Purchase of MCN Stock                                       92
                                                                                  
                      Article XIV.  Miscellaneous                                 
                      ---------------------------                                 
                                                                                  
   14.1               Beneficiary Designation                                     93
   14.2               Incompetency                                                94
   14.3               Expenses                                                    95
   14.4               Nonassignability                                            95
   14.5               Employment Noncontractual                                   95
   14.6               Merger or Consolidation with Another Plan                   95
   14.7               Continuance by a Successor                                  96
   14.8               Elimination of Certain Provisions                           97
</TABLE>



                                     -iv-

 
<PAGE>   6


                                    MICHCON
                      INVESTMENT AND STOCK OWNERSHIP PLAN
           (As Amended and Restated Effective as of January 1, 1989)

                              Article I.  The Plan

        1.1      Establishment and Amendment of the Plan.  Michigan
Consolidated Gas Company which is also known as MichCon (hereinafter referred
to as the "Company") presently maintains an investment and stock ownership plan
for the benefit of its Eligible Employees and the Eligible Employees of its
participating Affiliated Companies.  The plan was last restated effective as of
April 1, 1989, and was amended from time to time thereafter.

The plan as previously restated established the MichCon Employee Stock
Ownership Plan for Union Employees ("ESOP") and incorporated the ESOP into the
Michigan Consolidated Gas Company Union Employee's Investment Plan to form the
MichCon Investment and Stock Ownership Plan.

The plan is hereby further amended and completely restated as set forth herein
effective as of January 1, 1989, except as otherwise provided herein or
required by law, and shall continue to be known as the "MichCon Investment and
Stock Ownership Plan" (the "Plan").  The ESOP provisions of the Plan shall be
effective as of April 1, 1989.

        1.2      Applicability of the Plan.  Except as otherwise specified
herein or required by law, the provisions of the Plan as amended and restated
herein effective as of January 1, 1989, shall be applicable only with respect
to Eligible Employees of an Employer in current employment on or after January
1, 1989, and their beneficiaries.

Any person who was covered under the Plan as in effect prior to January 1,
1989, and whose employment terminated under the Plan



                                     -1-

 
<PAGE>   7


prior to January 1, 1989, shall continue to have his rights to receive benefits
determined under the provisions of the Plan in effect when his employment
relationship so terminated.

        1.3      Purpose and Type of Plan.  The purpose of the Plan is to
provide a convenient way for Participants to save on a regular and long-term
basis for their retirement income needs; to recognize the contribution made to
the Employer's successful operation by its employees and to reward such
contribution for those employees who qualify as participants under the terms of
the Plan; and to facilitate ownership of MCN Stock by participating Eligible
Employees.

The non-ESOP portion of the Plan is intended to qualify as a profit-sharing
plan and the ESOP portion of the Plan is intended to qualify as a stock bonus
and an employee stock ownership plan for purposes of Code sections 401(a), 402,
412, 417, 4975, and related provisions.



                                     -2-

 
<PAGE>   8


                            Article II.  Definitions

        2.1      Definitions.  Whenever used in the Plan, the following words
and phrases shall have the respective meanings stated below unless a different
meaning is plainly required by the context.
        (a)      "Accounting Period" means a period of one calendar month
                 except that the first accounting period shall commence with
                 the date on which the Plan first becomes effective with
                 respect to any Employer and end on the last day of the
                 calendar month in which such effective date occurs.
        (b)      "Actual Deferral Percentage" means the ratio (expressed as a
                 percentage) of the Elective Deferrals of an Employee who is
                 eligible to participate in the Plan for a Plan Year to the
                 Compensation of that Employee for such Plan Year.
        (c)      "Affiliated Company" means--
                 (1)     any corporation other than the Company, i.e., either a
                         subsidiary corporation or an affiliated or associated
                         corporation of the Company, which together with the
                         Company is a member of a "controlled group" of
                         corporations (as defined in Code section 414(b));
                 (2)     any organization which together with the Company is
                         under "common control" (as defined in Code section
                         414(c));
                 (3)     any organization which together with the Company is an
                         "affiliated service group" (as defined in Code section
                         414(m)); or
                 (4)     any other entity required to be aggregated with the
                         Company pursuant to Regulations under Code section
                         414(o).
        (d)      "Anniversary Date" means with respect to each Employee, the
                 anniversary each year of the first day of the first Accounting
                 Period coincident with or next following the Employee's first
                 Hour of Employment.  If an Employee whose employment was
                 terminated is reemployed but prior




                                     -3-
 
<PAGE>   9


                 to his reemployment he incurs a Break in Service Year or
                 following his reemployment he incurs a Break in Service Year
                 before completing a Year of Service, his Anniversary Date
                 shall be based upon his first Hour of Employment coincident
                 with or next following his date of reemployment; otherwise,
                 his Anniversary Date shall not be changed.
        (e)      "Annual Addition" means the amount allocated to a
                 Participant's account as such term is defined in section
                 4.11(a). 
        (f)      "Average Actual Deferral Percentage" means the average
                 (expressed as a percentage) of the Actual Deferral Percentages
                 of the Employees in a group who are eligible to participate in
                 the Plan for a Plan Year.
        (g)      "Break in Service Year" means a 12-month period described in
                 section 3.6.
        (h)      "Code" means the Internal Revenue Code of 1986, as amended.
        (i)      "Company" means Michigan Consolidated Gas Company.
        (j)      "Compensation" means a Participant's pay, determined as
                 follows:
                 (1)     For all purposes of the Plan, except as otherwise
                         specified in (2) or (3) below or required by the
                         context, Compensation means Eligible Compensation.
                 (2)     For purposes of satisfying the limits on contributions
                         described in section 4.8 (ADP test) and applying the
                         limits of section 415 of the Code as described in
                         section 4.11, Compensation includes all of the items
                         listed below as includible (to the extent applicable)
                         and excludes all of the items listed below as
                         excludable (to the extent applicable) on a Plan Year
                         basis:




                                     -4-
 
<PAGE>   10


                         (A)      Includible.
                                  (i)     The Employee's wages, salaries, fees,
                                          for professional services, and other
                                          amounts received (without regard to
                                          whether or not an amount is paid in
                                          cash) for personal services actually
                                          rendered in the course of employment
                                          with the Employer and any Affiliates
                                          to the extent that the amounts are
                                          includible in gross income including,
                                          but not being limited to, commissions
                                          paid salesmen, compensation for
                                          services on the basis of a percentage
                                          of profits, commissions on insurance
                                          premiums, tips, bonuses, fringe
                                          benefits, and reimbursements or other
                                          expense allowances under a
                                          nonaccountable plan (as described in
                                          Treasury regulation section
                                          1.62-2(c));
                                 (ii)     Amounts described in Code sections
                                          104(a)(3), 105(a), and 105(h), but
                                          only to the extent that these amounts
                                          are includible in the Employee's
                                          gross income;
                                (iii)     Amounts paid or reimbursed by the
                                          Employer or any Affiliate for moving
                                          expenses incurred by the Employee,
                                          but only to the extent that at the
                                          time of the payment it is reasonable
                                          to believe that these amounts are not
                                          deductible by the Employee under Code
                                          section 217;
                                 (iv)     The value of a nonqualified stock
                                          option granted to an Employee by the
                                          Employer or any Affiliate, but only
                                          to the extent that the value of the
                                          option is



                                     -5-

 
<PAGE>   11


                                          includible in the Employee's gross
                                          income for the taxable year in which
                                          it is granted; and 
                                  (v)     The amount includible in an
                                          Employee's gross income upon making
                                          the election described in Code
                                          section 83(b).
                                  Compensation under clause (i) includes
                                  foreign earned income as defined in Code
                                  section 911(b), whether or not excludable
                                  from gross income under Code section 911.

                                  Compensation under clause (i) is to be
                                  determined without regard to the exclusions
                                  from gross income in Code sections 931 and
                                  933.
                         (B)      Excludable.
                                  (i)     Contributions made by the Employer or
                                          any Affiliate to a plan of deferred
                                          compensation to the extent that,
                                          before the application of the Code
                                          section 415 limitations to that plan,
                                          the contributions are not includible
                                          in the Employee's gross income for
                                          the taxable year in which they are
                                          contributed;
                                 (ii)     Contributions made by the Employer or
                                          any Affiliate on an Employee's behalf
                                          to a simplified employee pension
                                          described in Code section 408(k)
                                          (such contributions are not
                                          considered as compensation for the
                                          taxable year in which contributed);
                                (iii)     Distributions from a plan of deferred
                                          compensation, regardless of whether
                                          such amounts are includible in the
                                          Employee's gross income when
                                          distributed, except that amounts
                                          received by an Employee




                                     -6-
 
<PAGE>   12


                                          pursuant to an unfunded, nonqualified
                                          plan are permitted to be considered
                                          as Compensation for Code section 415
                                          purposes in the year in which the
                                          amounts are includible in the
                                          Employee's gross income;
                                 (iv)     Amounts realized from the exercise of
                                          a nonqualified stock option, or when
                                          restricted stock (or property) held
                                          by an Employee either becomes freely
                                          transferable or is no longer subject
                                          to a substantial risk of forfeiture
                                          within the meaning of Code section 83
                                          and regulations thereunder;
                                  (v)     Amounts realized from the sale,
                                          exchange, or other disposition of
                                          stock acquired under a qualified
                                          stock option; and
                                 (vi)     Other amounts which receive special
                                          tax benefits, such as premiums for
                                          group-term life insurance (but only
                                          to the extent that the premiums are
                                          not includible in the Employee's
                                          gross income).
                 (3)     For purposes of determining whether an individual is a
                         Highly Compensated Employee, Compensation means an
                         Employee's Compensation as defined in paragraph (2) of
                         this section 2.1(j) but without regard to Code
                         sections 125, 402(a)(8), and 402(h)(1)(B) (i.e., with
                         the addition of elective deferrals pursuant to a
                         cafeteria plan, a cash-or-deferred arrangement, or a
                         simplified employee pension).
                 For Plan Years beginning on or after January 1, 1989 and prior
                 to January 1, 1994, the Compensation of each Employee that may
                 be taken into account under the Plan, except for purposes of
                 section 4.11 (Code section 415



                                     -7-

 
<PAGE>   13


                 limits), shall not exceed the first $200,000 of an Employee's
                 Compensation (as adjusted by the Secretary of the Treasury
                 under Code section 415(d)).  For Plan Years beginning on or
                 after January 1, 1994, the Compensation of each Employee that
                 may be taken into account under the Plan, except for purposes
                 of section 4.11, shall not exceed the first $150,000 of an
                 Employee's Compensation (as adjusted pursuant to Code section
                 401(a)(17)).  For purposes of the preceding two sentences, if
                 an Employee is a 5-percent owner of the Employer or one of the
                 ten Highly Compensated Employees paid the greatest
                 Compensation during the year, then any Compensation paid to
                 the spouse of such Employee or to any lineal descendants of
                 such Employee who have not attained age 19 before the close of
                 the year (and any applicable contribution on behalf of any
                 such individual) shall be treated as if it were paid to (or on
                 behalf of) such Employee.
        (k)      "Compensation Rate" means the amount of an Employee's Eligible
                 Compensation per pay period determined under uniform rules
                 established by the Company and before recognition of any
                 Salary Reduction allotment or cafeteria plan election.
        (l)      "Disability Retirement Date" means the date a Participant--
                 (1)     becomes eligible to receive benefits under a long-term
                         disability plan maintained by the Employer, or
                 (2)     is determined by the Company to be totally and
                         permanently disabled.  
                 In determining whether a Participant is totally and permanently
                 disabled, the Company may, in its discretion, rely on the
                 opinion of a physician selected by the Company to assist it in
                 making such a determination. 
        (m)      "Early Retirement Date" means the first day of any month prior
                 to a Participant's Normal Retirement Date
 

                                     -8-


 
<PAGE>   14


                 on which he terminates his employment by giving at least 60
                 days' written notice to the Company of his intention to retire
                 after he has attained age 55 and the sum of his attained age
                 and the number of his full Years of Service is at least 70.
        (n)      "Elective Deferrals" means Salary Reduction allotments under
                 section 4.1(a) and contributions under other plans maintained
                 by the Company or an Affiliated Company that constitute
                 elective deferrals within the meaning of Code section
                 402(g)(3).
        (o)      "Eligible Compensation" means the regular basic salary or wage
                 paid to an Employee by the Employer before any payroll
                 deduction for taxes or any other purpose, and before any
                 Salary Reduction allotment or cafeteria plan election, but
                 excluding bonuses, awards, shift differentials, severance
                 payments, differential payments made by reason of the
                 Employee's entry into Military Service, all amounts paid for
                 work in excess of 40 hours in any one week, all overtime or
                 other premium paid for work in excess of a maximum number of
                 hours in any one day, for work on holidays or for any other
                 reason, payments for so-called fringe benefits such as
                 Employer contributions to this Plan or any pension or
                 retirement plan, increased wages or salary resulting from
                 temporary promotion, upgrading or transfer, of whatever
                 duration, to a higher paid job or classification, and any
                 other premium, auxiliary, or special pay of any sort
                 whatsoever.

                 For Plan Years beginning on or after January 1, 1989 and prior
                 to January 1, 1994, the Eligible Compensation of an Employee
                 for purposes of the Plan shall not exceed $200,000; provided,
                 however, that such limit shall be adjusted as provided in Code
                 section 415(d).  For Plan Years beginning on or after
                 January 1, 1994, the Eligible Compensation of each Employee
                 that may be taken into account under the Plan, except for
                 purposes



                                     -9-

 
<PAGE>   15


                 of section 4.11, shall not exceed the first $150,000 of an
                 Employee's Compensation (as adjusted pursuant to Code section
                 401(a)(17)).  For purposes of the preceding two sentences, if
                 an Employee is a 5-percent owner of the Employer or one of the
                 ten Highly Compensated Employees paid the greatest
                 Compensation during the year, any Compensation paid to the
                 spouse of such Employee or to any lineal descendants of such
                 Employee who have not attained age 19 before the close of the
                 year (and any applicable contribution on behalf of any such
                 individual) shall be treated as if it were paid to (or on
                 behalf of) such Employee.
        (p)      "Eligible Employee" means an Employee of an Employer whose
                 terms and conditions of employment are covered by an agreement
                 with a collective bargaining agent which agreement permits
                 participation in this Plan.
        (q)      "Employee" means an individual who is an employee of the
                 Company or an Affiliated Company.
        (r)      "Employee Post-1986 Voluntary Deduction Account" means an
                 Employee's Voluntary Deduction allotments after December 31,
                 1986, and investment gains and losses therefrom.
        (s)      "Employee Pre-1987 Voluntary Deduction Account" means an
                 Employee's Voluntary Deduction allotments before January 1,
                 1987, and investment gains and losses therefrom.
        (t)      "Employee Salary Reduction Account" means an Employee's Salary
                 Reduction allotments, and investment gains and losses
                 therefrom.
        (u)      "Employer" means the Company and any Affiliated Company which
                 has adopted the Plan with the consent of the Company and in
                 the manner prescribed in section 12.1 and any successor
                 corporation which shall adopt the Plan pursuant to section
                 14.7.  If any such corporation shall withdraw from
                 participation in the Plan in accordance with section 12.2, the
                 term Employer shall not thereafter include such corporation.



                                     -10-

 
<PAGE>   16


        (v)      "Employer Salary Reduction Account" means the Employer
                 contributions to the Salary Reduction Account of an Employee
                 pursuant to section 4.2, and investment gains and losses
                 therefrom.
        (w)      "Employer Voluntary Deduction Account" means the Employer
                 contributions to the Voluntary Deduction Account of an
                 Employee pursuant to section 4.2, and investment gains and
                 losses therefrom.
        (x)      "ERISA" means the Employee Retirement Income Security Act of
                 1974, as amended.
        (y)      "ESOP" means the employee stock ownership plan established
                 pursuant to section 13.1.  
        (z)      "ESOP Account" means the account established and maintained on
                 behalf of each Participant in accordance with sections
                 8.1(c) and (d) and 13.2.
       (aa)      "Excess Contributions" means the amount described in section
                 4.10(a).
       (bb)      "Excess Deferrals" means the portion of Elective Deferrals for
                 a calendar year, if any, described in section 4.9.
       (cc)      "Family Member" means an individual described as a family
                 member in Code section 414(q)(6).
       (dd)      "Highly Compensated Employee" means, with respect to any Plan
                 Year, any Employee who at any time during the preceding
                 Plan Year (or such other period as the Company may elect
                 pursuant to Treasury regulations)--
                 (1)     received Compensation (as defined in section 2.1(j)(3)
                         of the Plan) from the Employer and all Affiliates in
                         excess of $75,000,
                 (2)     received Compensation (as defined in section 2.1(j)(3)
                         of the Plan) from the Employer and all Affiliates in
                         excess of $50,000 and was in the top-paid 20 percent
                         of Employees,
                 (3)     was an officer who received Compensation (as defined
                         in section 2.1(k)(3) of the Plan) from the


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<PAGE>   17


                         Employer and all Affiliates in excess of the amount in
                         effect under Code section 415(b)(1)(A) for the
                         preceding Plan Year, or
                 (4)     was a 5-percent owner.
                 Unless the Company makes the "calendar year calculation
                 election" under Treasury regulations, Highly Compensated
                 Employee also means, with respect to any Plan Year, any
                 Employee who, at any time during that Plan Year, met the
                 descriptions contained in paragraph (1), (2), or (3) and was
                 among the top-paid 100 Employees or any Employee who was a
                 5-percent owner.

                 A Family Member of a Highly Compensated Employee and a former
                 employee shall be treated as a Highly Compensated Employee to
                 the extent required by sections 414(q)(6) and (9) of the Code
                 and the regulations thereunder.

                 The dollar limits described in paragraphs (1), (2), and (3)
                 will be adjusted to reflect increases in the cost of living,
                 in the manner and at the times prescribed by the Secretary of
                 the Treasury.
         (ee)    "Hour of Employment" means an hour for which an individual
                 receives credit pursuant to section 3.7.
         (ff)    "Investment Plan Account" means the total value of an
                 Employee's Salary Reduction Account and Voluntary Reduction
                 Account.
         (gg)    "MCN Stock" means common stock of MCN Corporation.
         (hh)    "Military Service" means service--
                 (1)     on active duty, in time of national or local
                         emergency, in the armed forces of the United States or
                         of any State thereof,
                 (2)     in the armed forces of the United States or of any
                         State thereof under any compulsory service law, or
                 (3)     in the armed forces of the United States or any of its
                         allies in time of war in which the United States is
                         engaged.




                                     -12-
 
<PAGE>   18


         (ii)    "Nonhighly Compensated Employee" means an Employee of the
                 Employer who is neither a Highly Compensated Employee nor a
                 Family Member of a Highly Compensated Employee who is a
                 5-percent owner of the Employer or one of the ten Highly
                 Compensated Employees paid the greatest Compensation during
                 the year.
         (jj)    "Normal Retirement Date" means the Participant's sixty-fifth
                 birthday, if such birthday falls on the first day of the
                 month; otherwise, the first day of the month next following
                 the month in which such birthday occurs.
         (kk)    "Participant" means an Employee who is participating in the
                 Plan in accordance with its provisions.
         (ll)    "Plan" means MichCon Investment and Stock Ownership Plan and
                 any amendments thereto or restatements thereof from time to
                 time adopted.
         (mm)    "Plan Account" means the total value of an Employee's
                 Investment Plan Account and ESOP Account.
         (nn)    "Plan Year" means the calendar year.
         (oo)    "Primark Corporation Stock" means common stock of Primark
                 Corporation.
         (pp)    "Regulations" means regulations issued by the Department of
                 Labor construing Title I of ERISA or by the Internal Revenue
                 Service construing the Code.
         (qq)    "Salary Reduction" means an election by a Participant to have
                 the Compensation Rate that would otherwise be payable reduced
                 and contributed by the Employer to the Plan as a regular
                 allotment on behalf of the Participant.
         (rr)    "Salary Reduction Account" means an Employee's Salary
                 Reduction allotments, related Employer matching contributions,
                 and investment gains and losses therefrom.
         (ss)    "Suspense Account" means the account used to reflect MCN Stock
                 acquired with loan proceeds pursuant to section 13.4.
             


                                     -13-

 
<PAGE>   19


        (tt)     "Trust" means the Trust created by agreement between the
                 Employers and the Trustee, as from time to time amended.
        (uu)     "Trust Agreement" means the agreement between the Employers
                 and the Trustee referred to in section 8.8.
        (vv)     "Trustee" means the Trustee hereinafter provided for in
                 section 8.8 or any successor Trustee.
        (ww)     "Valuation Date" means the last day of each Accounting Period
                 on which the New York Stock Exchange shall be open for
                 business.
        (xx)     "Vesting Requirement" means the requirement for vesting
                 described in section 5.2.
        (yy)     "Voluntary Deduction" means an Employee's payroll deduction
                 allotments other than Salary Reduction allotments.
        (zz)     "Voluntary Deduction Account" means an Employee's Voluntary
                 Deduction allotments, related Employer matching contributions,
                 and investment gains and losses therefrom.
       (aaa)     "Years of Service" means year(s) of employment of an Employee
                 by an Employer or nonparticipating Affiliated Company as such
                 term is defined in section 3.5.

        2.2      Construction.  Unless the context clearly requires otherwise--
        (a)      the masculine pronoun whenever used shall include the
                 feminine, the singular shall include the plural, and vice
                 versa, and
        (b)      headings of Articles and sections herein are included solely
                 for convenience, and if there is any conflict between such
                 headings and the text of the Plan, the text shall control.





 
                                     -14-
<PAGE>   20


                    Article III.  Participation and Service

        3.1      Eligibility Requirements.
        (a)      Each individual who was eligible to participate in the Plan on
                 December 31, 1988, in accordance with the terms of the Plan in
                 effect on said date shall continue to be eligible to
                 participate, subject to the provisions of this Plan.  Each
                 other Employee shall become eligible to participate on the
                 first day of the first Accounting Period coincident with or
                 next following the latest to occur of--
                 (1)     the date he is employed as an Eligible Employee,
                 (2)     the date on which he completes at least one year of
                         eligibility service (as defined in section 3.1(b)), or
                 (3)     the date on which he attains age 21;
                 provided he is employed as an Eligible Employee on such date.
        (b)      For purposes of this Article III, a year of eligibility
                 service shall mean the 12-month period beginning on the date
                 of an Employee's first Hour of Employment, or the 12-month
                 period beginning on an Employee's Anniversary Date during
                 which he completes at least 1,000 Hours of Employment.

        3.2      Eligibility Upon Merger or Reemployment.  Any Employee who is
a Participant in any plan which is merged into this Plan shall become a
Participant in this Plan immediately upon the effective date of the merger.
Such an Employee shall be eligible to actively participate in this Plan in
accordance with section 3.4.

If a Participant's employment is terminated and he is thereafter reemployed
before incurring a Break in Service Year, he shall be eligible again to
actively participate in the Plan commencing with the first day of the first
Accounting Period coincident with or next following his date of reemployment.
In the event



                                     -15-

 
<PAGE>   21


such Participant does incur a Break in Service Year, he shall be eligible again
to actively participate in the Plan commencing with the first day of the first
Accounting Period coincident with or immediately preceding the day on which he
is reemployed after he has again satisfied the eligibility requirement of
section 3.1(a).

        3.3      Collective Bargaining Agency.  Effective January 14, 1991, if
any Employee shall become a Participant in the Plan and shall thereafter cease
to be represented by a collective bargaining agency pursuant to a collective
bargaining agreement between his Employer and the collective bargaining agency
representing such Employee, he shall nevertheless continue to be eligible to
actively participate in the Plan until such time as the terms and conditions of
his employment are no longer governed by such a collective bargaining
agreement.

If such an Employee becomes eligible to participate in the MichCon Savings and
Stock Ownership Plan or any successor plan, his entire Plan Account shall be
transferred to such plan and the Employee shall no longer be eligible to
participate in this Plan.  The foregoing sentence shall be applicable as of
January 14, 1991 for all Employees who thereafter become eligible to
participate in the MichCon Savings and Stock Ownership Plan, and as of the date
agreed upon by the Employee if the Employee became eligible to participate in
the MichCon Savings and Stock Ownership Plan prior to January 14, 1991,
irrespective of their date of transfer.  Effective as of April 1, 1989, the
Participant's Plan Account shall be fully vested upon such transfer.

        3.4      Applications.  An Employee who is eligible to participate on
the date the Plan becomes effective with respect to his Employer may become a
Participant commencing with such effective date by filing a written application
with his Employer in the form prescribed by the Company not later than 20 days
after such effective date.  Thereafter, an Eligible Employee may become a
Participant by filing a written application with his



                                     -16-

 
<PAGE>   22


Employer in the form prescribed by the Company at least 20 days prior to the
date upon which his participation is to commence.  The Employee's application
shall authorize the Employer to deduct allotments from the Employee's Eligible
Compensation in amounts specified by the Employee pursuant to Article IV, and
to have allotments made as a Salary Reduction pursuant to Article IV.  The
application shall evidence the Employee's acceptance of and agreement to all of
the provisions of the Plan.

        3.5      Years of Service.  An Employee shall be credited for Years of
Service for his period of employment with the Employer and each
nonparticipating Affiliated Company, determined as follows:
        (a)      An Employee shall receive credit, for purposes of vesting, for
                 all Years of Service.  An Employee shall have one "Year of
                 Service" for each 12-month period beginning on the date of the
                 Employee's first Hour of Employment and on each subsequent
                 Anniversary Date, during which the Employee completes 1,000 or
                 more Hours of Employment.
        (b)      Years of Service shall not be interrupted--
                 (1)     by any transfer of employment of an Employee between
                         Affiliated Companies regardless of whether the
                         Affiliated Company is an Employer hereunder; or
                 (2)     during such period as an Employee is receiving credit
                         for Hours of Employment under section 3.7.
        (c)      If an Employee is reemployed following a Break in Service
                 Year, he shall be considered a new Employee for purposes of
                 the Plan, except--
                 (1)     If prior to such Break in Service Year he had a vested
                         interest in his ESOP Account, Employer Salary
                         Reduction Account, or Employer Voluntary Deduction
                         Account, Years of Service he had prior to the Break in
                         Service Year shall be reinstated after such Employee
                         completes a Year of Service after such Break in
                         Service Year.

                                     -17-



 
<PAGE>   23


                 (2)     If section 3.5(c)(1) is not applicable, and if the
                         Employee's number of consecutive Break in Service
                         Years does not equal or exceed the greater of five or
                         the number of Years of Service he had before incurring
                         a Break in Service Year, the Years of Service he had
                         prior to such Break in Service Years shall be
                         reinstated after such Employee completes a Year of
                         Service after such Break in Service Years.
        (d)      Notwithstanding the foregoing provisions, an Employee's Years
                 of Service shall exclude any Years of Service completed before
                 an Employee attains age 18.

        3.6      Break in Service Year.  "Break in Service Year" shall mean a
12-month period beginning on an Employee's Anniversary Date during which the
Employee has not completed more than 500 Hours of Employment (as defined in
section 3.7).  Notwithstanding the foregoing, the following periods shall not
be deemed to be Break in Service Years:
        (a)      If a Participant retires on his Disability Retirement Date,
                 thereafter ceases to be totally and permanently disabled, and
                 returns to the employ of an Employer, the period between his
                 Disability Retirement Date and the date as of which he ceases
                 to be totally and permanently disabled.
        (b)      If a Participant commences receiving benefits under a
                 long-term disability benefit program maintained by an Employer
                 and thereafter ceases to receive benefits under such program
                 and returns to the employ of the Employer, the period during
                 which he was receiving benefits under such program.
If an Employee incurs a Break in Service Year and prior to such Break in
Service Year has not completed five Years of Service, his Years of Service
completed prior to such a Break in Service Year shall be disregarded unless he
completes a Year of Service after such Break in Service Year and before the
total of such Break in Service Year and any ensuing consecutive Break in


                                     -18-


 
<PAGE>   24


Service Years equals the greater of five or the number of his Years of Service
(as defined in section 3.5 but without excluding Years of Service completed
prior to attaining age 18) prior to such Break in Service Year.

        3.7      Hours of Employment.  "Hours of Employment" shall mean, for
any individual performing or who has performed services for one or more
Employers or nonparticipating Affiliated Companies, the sum of the following:
        (a)      All hours for which the individual is directly or indirectly
                 paid or entitled to payment by an Employer or nonparticipating
                 Affiliated Company for the performance of duties.  These hours
                 shall be credited to the individual for the computation period
                 or periods in which the duties are performed.
        (b)      Except as provided in section 3.7(e) below, all hours for
                 which the individual is directly or indirectly paid or
                 entitled to payment by an Employer or nonparticipating
                 Affiliated Company for reasons (such as vacation, holiday,
                 sickness, incapacity, layoff, jury duty, leave of absence,
                 Military Service, or disability) other than for the
                 performance of duties.  These hours shall be credited to the
                 individual for the computation period or periods in which the
                 period during which no duties are performed occurs, beginning
                 with the first unit of time to which the payment relates.
        (c)      All hours for which back pay, irrespective of mitigation of
                 damages, has been awarded, agreed to, or paid by an Employer
                 or nonparticipating Affiliated Company, with no duplication of
                 credit for hours.  These hours shall be credited to the
                 individual for the computation period or periods to which the
                 award or agreement pertains rather than the computation period
                 in which the award, agreement, or payment is made.
        (d)      Except as provided in section 3.7(e) below, eight Hours of
                 Employment per day for each working day that an


                                     -19-


 
<PAGE>   25


                 individual is absent from work without pay for an approved
                 leave of absence, voluntary time, sick time, disciplinary
                 layoff, or Military Service if the individual returns to the
                 employ of an Employer or nonparticipating Affiliated Company
                 within 90 days after the end of such period.  These hours
                 shall be credited to the individual for the computation period
                 or periods in which the period during which no duties are
                 performed occurs, beginning with the first such period.
        (e)      Eight Hours of Employment per day for each working day that an
                 individual is absent from work with or without pay because of
                 pregnancy of the individual, birth of a child to the
                 individual, placement of a child with the individual in
                 connection with the adoption of such child by such individual,
                 or caring for such child for a period beginning immediately
                 following such birth or placement.  The Company may, in its
                 discretion, request such information from the individual as
                 the Company shall deem relevant in order to verify that an
                 absence is for the reasons described in this subsection (e).

                 Notwithstanding the foregoing, no more than 501 Hours of
                 Employment shall be credited under this subsection (e) on
                 account of any such pregnancy or placement if the individual
                 does not return to the employ of an Employer or participating
                 Affiliated Company within 90 days after the end of the period
                 approved for such absence.  Hours credited under this
                 subsection (e) shall be credited to the individual only in the
                 year in which the absence begins if the crediting is necessary
                 to prevent a Break in Service Year for such year; or, in any
                 other case, in the immediately following year; provided,
                 however, that if more than 501 hours are credited under this
                 subsection (e) on account of any



                                     -20-

 
<PAGE>   26


                  such pregnancy or placement, the excess over 501 hours shall
                  be credited to the period or periods to which it relates.
Hours of Employment credited under this section 3.7 shall comply with the rules
set forth in 29 C.F.R. section 2530.200b-2(b) and (c), which rules are hereby
incorporated by reference.

        3.8      Employment by Related Entities.  If an Employee's employer is
a nonparticipating Affiliated Company, any period in which the Employee is
employed by the nonparticipating Affiliated Company, while such membership or
common control as defined in section 2.1(c) exists, shall be taken into account
for purposes of satisfying the eligibility service requirement set forth in
section 3.1 and measuring such Employee's Years of Service to the same extent
it would have been had such period of employment been employment by an
Employer.

        3.9      Leased Employees.  A person who is not an Employee of an
Employer or nonparticipating Affiliated Company and who performs services for
an Employer or a nonparticipating Affiliated Company pursuant to an agreement
between the Employer or nonparticipating Affiliated Company and a leasing
organization shall be considered a "leased employee" if such person performed
the services on a substantially full-time basis for a year and the services are
of a type historically performed by employees.  A person who is considered a
"leased employee" of an Employer or nonparticipating Affiliated Company shall
not be considered an Employee for purposes of participating in this Plan or
receiving any contribution or benefit under this Plan.  A leased employee shall
be excluded from this Plan regardless of whether the leased employee
participates in any plan maintained by the leasing organization.  However, if a
leased employee participates in the Plan as a result of subsequent employment
with an Employer, his previous service as a leased employee shall be counted in
calculating his Years of Service.  Notwithstanding the preceding provisions of
this section 3.9, a leased employee will be


                                     -21-


 
<PAGE>   27


included as an Employee for purposes of applying the requirements described in
Code section 414(n)(3) and for purposes of determining the number and identity
of Highly Compensated Employees.


                                     -22-


 
<PAGE>   28


                           Article IV.  Contributions

        4.1      Employee Allotments.
        (a)      Amount of Allotments.  Each Participant may make a regular
                 allotment to the Plan.  Such allotment shall not be less than
                 1 percent nor more than the amount determined as follows:
                 (1)     A Participant represented by S.E.I.U. Local 80
                         (Detroit) and P.T. & S. and I.C.W.U. Local 799
                         (P.T. & S.) may make allotments up to a percentage of
                         his Compensation Rate, in incremental percentages of 1
                         percent, determined as follows:

                                Period                        Percentage
                        -----------------------               ----------

                        Prior to April 1, 1992                   10%
                                                              
                        April 1, 1992 -                       
                          August 31, 1993                        14%

                        September 1, 1993 and later              15%

                 (2)     A Participant represented by I.C.W.U. Local 70, 132,
                         and 799 (Northern) may make allotments up to
                         a percentage of his Compensation Rate, in incremental
                         percentages of 1 percent, determined as follows:

                                 Period                          Percentage
                        -------------------------                ----------

                        Prior to January 1, 1990                       8%
                                                                
                        January 1, 1990 -                       
                          August 31, 1992                             10%
                                                                
                        September 1, 1992                       
                          and later                                   14%

                 Allotments will be effected by Voluntary Deductions, Salary
                 Reductions, or any combination thereof, as elected by the
                 Participant.  The amount of such Voluntary Deductions or
                 Salary Reductions shall be transferred to the Trustee after
                 each pay period; provided, however, that a Participant's
                 Salary Reduction allotments (A) shall be limited as provided



                                     -23-

 
<PAGE>   29


                 in section 4.8 and (B) shall not exceed a percentage of the
                 Participant's Compensation Rate determined as follows:
                 (i)     In the case of Participants referred to in (1) above--

                                Period                             Percentage
                        -----------------------                    ----------

                        Prior to April 1, 1992                         6%
                                                                    
                        April 1, 1992 -                             
                          August 31, 1993                              8%
                                                                    
                        September 1, 1993                              9%
                (ii)     In the case of Participants referred to in (2) above--

                                  Period                           Percentage
                        ---------------------------                ----------
                                                                   
                        Prior to September 1, 1992                     6%

                        September 1, 1992 and later                    8%

                 Notwithstanding the foregoing, the Company may, in its sole
                 discretion, (1) reduce the Salary Reduction allotments
                 permitted by a group of Participants if, in the opinion of the
                 Company, it is advisable to do so in order to satisfy the
                 requirements of section 4.8 or 4.11; or (2) reduce the
                 Voluntary Deduction allotments permitted by a group of
                 Participants if, in the opinion of the Company, it is
                 advisable to do so in order to satisfy the requirements of
                 section 4.11.
        (b)      Changes in Allotments.  The allotment of Voluntary Deductions
                 and/or Salary Reductions designated by a Participant shall
                 continue in effect, notwithstanding any change in his
                 Compensation Rate, until the Participant shall change such
                 allotment; provided, however, that such allotment shall in no
                 event be less than 1 percent, nor more than the limits of
                 section 4.1(a)(1) and (2), in incremental percentages of
                 1 percent.

                                     -24-



 
<PAGE>   30


                 A Participant may change his allotment--
                 (1)     prior to August 1, 1991, as of the first day of any
                         Accounting Period, or
                 (2)     on or after August 1, 1991, but prior to December 1,
                         1993, as of the first day of any calendar quarter, or
                 (3)     on or after December 1, 1993, as of the first day of
                         any month,
                 by giving written directions to his Employer in the form
                 prescribed by the Company at least 20 days prior to the
                 effective date of the change.  Prior to August 1, 1991, such
                 changes may be made only once in each calendar year, except
                 that any time a Participant's Compensation Rate is changed he
                 shall have the right to change his allotment as of the first
                 day of any Accounting Period commencing not more than 60 days
                 thereafter by giving 20 days' written notice to his Employer
                 in the form prescribed by the Company.
        (c)      Voluntary Suspension of Allotments.  Any Participant may, by
                 giving 20 days' written notice to his Employer in the form
                 prescribed by the Company, suspend his allotment of Voluntary
                 Deductions and/or Salary Reductions, effective as of the end
                 of any Accounting Period, either indefinitely or for any
                 specified period provided that in either case the suspension
                 shall be for at least 12 full Accounting Periods.  In case of
                 any such suspension of any allotments, the Employer's
                 contributions on behalf of the Participant shall be
                 automatically suspended for a like period.
        (d)      Automatic Suspension of Allotments.  A Participant's
                 allotments of Voluntary Deductions and Salary Reductions and
                 the Employer's contributions on behalf of the Participant
                 shall be suspended automatically for any period during which
                 the Participant is absent without pay under any of the
                 circumstances described in section 3.7(c), (d), or (e), and
                 such an absence shall not constitute termination of service
                 for purposes of




                                     -25-
 
<PAGE>   31


                 any of the provisions of Article IX.  A Participant may, by
                 giving 20 days' written notice to his Employer in the form
                 prescribed by the Company, suspend his allotment of Voluntary
                 Deductions and/or Salary Reductions for any period during
                 which he is absent from work under any of the circumstances
                 described in section 3.7(b) or (c) and receiving Compensation
                 at a reduced Compensation Rate, in which case the Employer
                 contributions on behalf of such Participant shall be
                 automatically suspended for a like period.

        4.2      Employer Investment Plan Contributions.  Each Employer shall
contribute, to the Salary Reduction Account of each of its participating
Employees, an amount equal to 25 percent of the Salary Reduction allotment of
such Participant; provided, however, that Salary Reduction allotments shall be
disregarded to the extent that they exceed an amount determined by multiplying
the applicable contribution percentage shown in the following schedules by the
Participant's Compensation Rate:
        (a)      Effective for periods prior to April 1, 1989 for Participants
                 represented by S.E.I.U. Local 80 (Detroit and P.T. & S.) and
                 I.C.W.U. Local 799 (P.T. & S.):

                                                             Contribution
                          Years of Service                    Percentage 
                        ----------------------               ------------

                        1 through 5                              2%
                        More than 5 through 10                   3%
                        More than 10                             4%

        (b)      Effective for periods prior to January 1, 1990, for
                 Participants represented by I.C.W.U. Locals 70, 132, and 799
                 (Northern):

                                                             Contribution
                          Years of Service                    Percentage 
                        ----------------------               ------------

                        1 through 5                              2%
                        More than 5 through 14                   3%
                        More than 14                             4%




                                     -26-
 
<PAGE>   32


        (c)      Effective April 1, 1989 for Participants referred to in (a)
                 and January 1, 1990 for Participants referred to in (b):

                                                             Contribution
                          Years of Service                    Percentage 
                        -----------------------              ------------

                        1 through 5                              2%
                        More than 5 through 10                   3%
                        More than 10 through 14                  4%
                        More than 14                             5%


        (d)      Effective September 1, 1993 for all Participants:

                                                             Contribution
                        Years of Service                      Percentage 
                        -----------------------              ------------

                        1 through 5                              2%
                        More than 5 through 10                   3%
                        More than 10 through 14                  4%
                        More than 14 through 25                  5%
                        More than 25                             6%


In addition, in cases where the Participant's Salary Reduction allotment is
less than the percentage of his Compensation Rate allowed in the above schedule
for his Years of Service, the Employer shall contribute to the Voluntary
Deduction Account of such participating Employee an amount equal to 25 percent
of the smaller of (1) the Participant's Voluntary Deduction allotment, or (2)
an amount equal to (A) the applicable contribution percentage, per the above
schedule, times the Participant's Compensation Rate, minus (B) the
Participant's Salary Reduction allotment.  The maximum Employer matching
contributions on behalf of any Participant shall not be increased until such
Participant has filed a new election form with the Company.

Notwithstanding the foregoing, until January 1, 1990, the Employer
contributions on behalf of the Participants represented by I.C.W.U.  Locals 70,
132, and 799 (Northern) shall be determined by substituting "100 percent" for
"25 percent" in each place that it appears in this section 4.2.



                                     -27-

 
<PAGE>   33


The Employer contributions pursuant to this section 4.2 (including the amount
of any Salary Reduction allotments made by Participants) shall be made only
from the current profits or retained earnings of the Employer.  The current
profits and accumulated retained earnings of the Employer shall be determined
in accordance with generally accepted accounting principles and practices and
shall be the amounts reflected in the Employer's certified financial
statements.

        4.3      Employer ESOP Contributions.
        (a)      Basic ESOP Contribution.  Subject to subsection (d) of this
                 section, effective on and after April 1, 1989, each Employer
                 shall contribute to the ESOP Account of each of its
                 participating Employees each pay period an amount equal to the
                 difference, if any, between (1) and (2) below:
                 (1)     75 percent of the sum of the Salary Reduction and
                         Voluntary Deduction allotments of such Participant for
                         such pay period; provided, however, that Salary
                         Reduction and Voluntary Deduction allotments shall be
                         disregarded to the extent that they exceed, in the
                         aggregate, an amount determined by multiplying the
                         applicable contribution percentage in the schedules
                         set forth in section 4.2 by such Participant
                         Compensation Rate.
                 (2)     The value of the shares of MCN Stock allocated to the
                         ESOP Account of such Participant pursuant to section
                         13.4(d) for such pay period.  The value of shares
                         allocated under section 13.4(d) shall be the market
                         value thereof as of the last day of the pay period for
                         which the shares are allocated, with the market value
                         to be determined by the Company in a nondiscriminatory
                         manner.
        (b)      Contribution of Principal, Interest, or Other Payments.  Each
                 Employer also shall contribute to the ESOP its proportionate
                 share of any additional amount necessary



                                     -28-

 
<PAGE>   34


                 to make principal, interest, or other payments required by the
                 terms of any loan made to the ESOP in accordance with section
                 13.4.  Each Employer's proportionate share shall be equal to
                 the proportion that its contributions under section 4.3(a)
                 bears to the total contributions under section 4.3(a).

                 Effective November 1, 1989, each Employer also may make
                 additional contributions to make principal, interest, or other
                 payments in accordance with the terms of any loan made to the
                 ESOP in accordance with section 13.4.
        (c)      Dividend-Related Contributions.  Effective November 1, 1989,
                 each Employer also shall contribute to the ESOP Account of
                 each of its participating Employees such amounts as may be
                 necessary to acquire for the ESOP Account of such Participant
                 shares of MCN Stock having a fair market value equal to the
                 amount of any dividends on shares of MCN Stock allocated to
                 the ESOP Account of such Participant that were used to repay
                 an ESOP loan in accordance with section 13.4(c).  Such
                 contributions shall be made on, or as soon as practicable
                 after, each date on which dividends on allocated shares of MCN
                 Stock are used to repay a loan.  In no event shall the shares
                 of MCN Stock acquired with contributions under this subsection
                 (c) be allocated to the ESOP Account of such Participant later
                 than the last day of the Plan Year during which (but for the
                 use of the dividend to repay the loan) the dividend giving
                 rise to such contribution would have been allocated to the
                 ESOP Account of such Participant.
        (d)      Exception.  Notwithstanding any other provision hereof, no
                 contributions shall be made prior to January 1, 1990 to the
                 ESOP Account of any Participant represented by I.C.W.U. Locals
                 70, 132, and 799 (Northern).



                                     -29-

 
<PAGE>   35


        4.4      Additional Employer Contributions.  Effective January 14,
1991, if a Participant receiving payments (based upon 40 or more hours per
week) under the terms of any Workers' Compensation law does not have sufficient
compensation to make Salary Reduction or Voluntary Deduction allotments in an
amount equal to the amount of the Participant's allotments as in effect during
the Participant's last period of active service, then the Participant's
Employer shall contribute on behalf of the Participant such additional amount
as would have been contributed by the Employer under sections 4.2 and 4.3 on
behalf of such Participant had the Participant's allotments been continued at
the rate in effect during the Participant's last period of active service.
Additional contributions under this section 4.4 shall be treated for accounting
purposes as if made under section 4.2 or 4.3, as applicable.

        4.5      Rollover Contributions.
        (a)      From Qualified Plan.  If an Employee receives, either before
                 or after becoming an Employee--
                 (1)     prior to January 1, 1993, a qualified total
                         distribution (within the meaning of Code section
                         402(a)(5)(E)) or,
                 (2)     effective January 1, 1993, an eligible rollover
                         distribution (within the meaning of Code section
                         402(c)(4))
                 from an employees' trust described in Code section 401(a)
                 which is exempt from tax under Code section 501(a) or from a
                 qualified annuity plan described in Code section 403(a) (other
                 than an employees' trust or an annuity plan under which the
                 Employee was an Employee within the meaning of Code section
                 401(c)(1) at the time contributions were made on his behalf
                 under such trust or annuity plan), then such Employee may
                 transfer and deliver to the Company, to be credited to his
                 Employee Salary Reduction Account as if it were a Salary
                 Reduction allotment, an amount which does not exceed the
                 amount of such qualified total distribution



                                     -30-

 
<PAGE>   36


                 or eligible rollover distribution (including any proceeds from
                 the sale of any property received as a part of such qualified
                 total distribution or eligible rollover distribution) less, in
                 the case of a qualified total distribution, the amount
                 considered contributed to such trust or annuity plan by the
                 Employee.
        (b)      From Individual Retirement Account or Annuity.  If--
                 (1)     an Employee receives, either before or after becoming
                         an Employee, a distribution or distributions from an
                         individual retirement account or individual retirement
                         annuity (within the meaning of Code section 408) or
                         from a retirement bond (within the meaning of Code
                         section 409);
                 (2)     no amount in such account, no part of the value of
                         such annuity, or no part of the value of the proceeds
                         of such bond is attributable to any source other
                         than--
                         (A)      prior to January 1, 1993, a qualified total
                                  distribution (within the meaning of Code
                                  section 402(a)(5)(E)), or
                         (B)      effective January 1, 1993, an eligible
                                  rollover distribution (within the meaning of
                                  Code section 402(c)(4))
                         from an employees' trust described in Code section
                         401(a) which is exempt from tax under Code section
                         501(a) or annuity plan described in Code section
                         403(a) (other than an employees' trust or an annuity
                         plan under which the Employee was an Employee within
                         the meaning of Code section 401(c) at the time
                         contributions were made on his behalf under such trust
                         or annuity plan) and any earnings on such a qualified
                         total distribution or eligible rollover distribution;
                         and

                                     -31-



 
<PAGE>   37


                 (3)     for rollovers prior to January 1, 1993, the amount
                         received represents the entire amount in such account,
                         the entire value of such annuity or the entire value
                         of such bond,
                 then such Employee may transfer and deliver to the Company, to
                 be credited to his Salary Reduction Account as if it were a
                 Salary Reduction allotment, such distribution or
                 distributions.
        (c)      Timing and Substantiation.  Any transfer and delivery pursuant
                 to this section 4.5 shall be delivered by the Employee to the
                 Company and by the Company to the Trustee on or before the
                 sixtieth day after the day on which the Employee receives the
                 distribution or on or before such later date as may be
                 prescribed by law.  Any such transfer and delivery must be
                 accompanied by--
                 (1)     a statement of the Employee that to the best of his
                         knowledge the amount so transferred meets the
                         conditions specified in this section 4.5, and
                 (2)     a copy of such documents as may have been received by
                         the Employee advising him of the amount and the
                         character of such distribution.
                 Notwithstanding the foregoing, the Company shall not accept a
                 rollover contribution if, in its judgment, such acceptance
                 would cause the Plan to violate any provision of the Code or
                 Regulations.
        (d)      Deemed Allotment for Certain Purposes.  A rollover
                 contribution pursuant to this section 4.5 shall be deemed to
                 be an allotment of a Participant for purposes of the value of
                 a Participant's fund account as provided in section 8.2 and in
                 determining the amount distributable to a Participant, the
                 provisions of Article IX that are applicable to Salary
                 Reduction allotments will be used, pursuant to section 9.1,
                 but not for purposes of determining the amount of the
                 contribution to be made on behalf of a Participant by his
                 Employer pursuant to section 4.2, 4.3, or 4.4 or calculating
                 the Annual Addition of such Participant.




                                     -32-
 
<PAGE>   38


        (e)      Deemed Participation for Certain Purposes.  If the amount of
                 rollover contribution is made by an Employee prior to his
                 becoming a Participant, such Employee shall, until such time
                 as he becomes a Participant, be deemed to be a Participant for
                 all purposes of the Plan except for purposes of any
                 determination of when he becomes a Participant pursuant to
                 section 3.1 and the making of allotments pursuant to section
                 4.1(a).

        4.6      Transfers from the MichCon Savings and Stock Ownership Plan.
Effective January 14, 1991, if an Employee who previously had participated in
the MichCon Savings and Stock Ownership Plan (the "Savings Plan") becomes a
Participant in the Plan and the Participant's plan account in the Savings Plan
is transferred to the Plan in accordance with section 3.3 of the Savings Plan,
the Plan shall accept such transfer.  Amounts transferred shall be 100 percent
vested at all times and shall be treated for all purposes in the same manner as
they were treated under the Savings Plan; that is:
        (a)      Amounts attributable to Employer salary reduction allotments
                 under the Savings Plan shall be allocated to the Participant's
                 Employee Salary Reduction Account;
        (b)      Amounts attributable to voluntary deduction allotments under
                 the Savings Plan shall be allocated to the Participant's
                 Employee Voluntary Deduction Account;
        (c)      Amounts attributable to Employer Savings Plan contributions
                 shall be allocated to the Participant's Employer Salary
                 Reduction Account or Employer Voluntary Deduction Account, as
                 the case may be; and
        (d)      Amounts transferred from the ESOP Account of the Participant
                 in the Savings Plan shall be allocated to the Participant's
                 ESOP Account.
Notwithstanding the foregoing, amounts transferred shall not be used for
purposes of determining the amount of the contribution to be made on behalf of
a Participant by the Employer pursuant to section 4.2, 4.3, or 4.4, or
calculating the Actual Deferral Percentage or Annual Addition of the
Participant.



                                     -33-

 
<PAGE>   39


        4.7      Transfers from the MichCon Employee Stock Ownership Plan.
        (a)      In General.  The Company has previously maintained the MichCon
                 Employee Stock Ownership Plan (the "Tax Credit ESOP"), which
                 was a plan separate and distinct from the MichCon Employee
                 Stock Ownership Plan for Union Employees which constitutes a
                 part of the Plan.  The Company terminated the Tax Credit ESOP
                 and, upon such termination, a portion of the assets of the Tax
                 Credit ESOP were transferred to this Plan.  The purpose of
                 this section 4.7, which is effective as of January_25, 1991,
                 is to set forth specific provisions applicable to the assets
                 so transferred.  In the event of any conflict between any
                 other provision of the Plan and this section 4.7 the terms of
                 this section 4.7 shall govern with respect to amounts
                 transferred from the Tax Credit ESOP, adjusted for earnings
                 and losses thereon.
        (b)      Allocation to ESOP Account.  All amounts transferred from the
                 Tax Credit ESOP attributable to Plan Years 1975 through 1982
                 on behalf of any Participant or former Participant who has an
                 account balance in this Plan shall be allocated to the ESOP
                 Account of such Participant or former Participant.  The
                 amounts transferred to the ESOP Account of a Participant or
                 former Participant, adjusted for any earnings or losses
                 thereon, shall, subject to the special rules set forth in this
                 section 4.7, be treated in the same manner as other assets of
                 the ESOP Accounts for all purposes of this Plan, including,
                 but not limited to, distributions, loans, investments, and
                 diversification of investments.  The amounts transferred shall
                 not be deemed to constitute an Employee Allotment or an
                 Employer Contribution for discrimination testing or any other
                 purpose.
        (c)      Allocation to MCN Salary Reduction Account.  All amounts
                 transferred from the Tax Credit ESOP


                                     -34-


 
<PAGE>   40


                 attributable to Plan Years 1983 through 1986 on behalf of any
                 Participant or former Participant who has an account balance
                 in this Plan shall be allocated to the Salary Reduction
                 Account of such Participant or former Participant.  The
                 amounts transferred to the Salary Reduction Account of a
                 Participant or former Participant, adjusted for any earnings
                 or losses thereon, shall, subject to the special rules set
                 forth in this section 4.7, be treated in the same manner as
                 other assets of the Salary Reduction Accounts for all purposes
                 of this Plan, including, but not limited to, distributions,
                 loans, investments, and diversification of investments.  The
                 amounts transferred shall not be deemed to constitute an
                 Employee Allotment or an Employer Contribution for
                 discrimination testing or any other purpose.
        (d)      Vesting.  All amounts transferred from the Tax Credit ESOP on
                 behalf of any Participant or former Participant, adjusted for
                 any earnings or losses thereon, shall at all times be fully
                 vested and nonforfeitable.

        4.8      Limitations on Salary Reduction Allotments.
        (a)      Dollar Limitation.  In no event shall any Employer make Salary
                 Reduction allotments for any calendar year, with respect to
                 any Participant in excess of $7,627 (for 1989) (as adjusted by
                 the Secretary of the Treasury to reflect increases in the cost
                 of living).  This limit shall be applied by aggregating all
                 plans and arrangements maintained by the Company and all
                 Affiliated Companies that provide for elective deferrals (as
                 defined in Code section 402(g)).
        (b)      ADP Test.  Effective for Plan Years beginning on or after
                 January 1, 1992, in addition to the limitations set forth
                 elsewhere in this Plan, one of the following tests must be
                 satisfied for the Plan Year:



                                     -35-

 
<PAGE>   41


                 (1)     The Average Actual Deferral Percentage for Highly
                         Compensated Employees who are eligible to participate
                         for the Plan Year shall not exceed the Average Actual
                         Deferral Percentage for Nonhighly Compensated
                         Employees who are eligible to participate for the Plan
                         Year multiplied by 1.25; or
                 (2)     The Average Actual Deferral Percentage for Highly
                         Compensated Employees who are eligible to participate
                         for the Plan Year shall not exceed the Average Actual
                         Deferral Percentage for Nonhighly Compensated
                         Employees who are eligible to participate for the Plan
                         Year multiplied by two, provided that the Average
                         Actual Deferral Percentage for such Highly Compensated
                         Employees does not exceed the Average Actual Deferral
                         Percentage for such Nonhighly Compensated Employees by
                         more than two percentage points.
        (c)      Determination of Actual Deferral Percentages.  For purposes of
                 the Actual Deferral Percentage test described in this section
                 4.8--
                 (1)     An Elective Deferral will be taken into account for a
                         Plan Year only if it relates to Compensation that
                         either would have been received by the Eligible
                         Employee in the Plan Year (but for the deferral
                         election) or is attributable to services performed by
                         the Eligible Employee in the Plan Year and would have
                         been received by the Eligible Employee within 2_1/2
                         months after the close of the Plan Year (but for the
                         deferral election);
                 (2)     An Elective Deferral will be taken into account for a
                         Plan Year only if it is allocated to the Eligible
                         Employee as of a date within that Plan Year.  For this
                         purpose, an Elective Deferral is considered allocated
                         as of a date within a Plan Year if the allocation is
                         not contingent on



                                     -36-

 
<PAGE>   42


                         participation or performance of services after such
                         date and the Elective Deferral is actually paid to the
                         Trust no later than 12 months after the Plan Year to
                         which the contribution relates;
                 (3)     The Actual Deferral Percentage for an Employee who is
                         eligible to participate shall be computed by treating
                         any Excess Deferral (as defined in section 4.9) as an
                         Elective Deferral, except to the extent provided by
                         Regulations;
                 (4)     The Actual Deferral Percentage for any Employee who is
                         a participant under two or more section 401(k) plans
                         or arrangements that are maintained by the Company or
                         an Affiliated Company shall be determined as if all
                         such Elective Deferrals were made under a single
                         arrangement; provided, however, that no Elective
                         Deferrals under an employee stock ownership plan (as
                         defined in Code section 4975(e)(7)) shall be taken
                         into account for purposes of this section 4.8;
                 (5)     In the event that two or more plans which include
                         cash-or-deferred arrangements are considered as one
                         plan for purposes of Code section 401(a)(4) or 410(b),
                         the cash-or-deferred arrangements included in such
                         plans shall be treated as one arrangement for purposes
                         of this section 4.8;
                 (6)     For purposes of determining the Actual Deferral
                         Percentage of an Employee who is a 5-percent owner of
                         the Company or one of the ten Highly Compensated
                         Employees paid the most Compensation during the year,
                         the Elective Deferrals and Compensation of such
                         Employee shall include the Elective Deferrals and
                         Compensation of Family Members, and such Family
                         Members shall be disregarded in determining the Actual
                         Deferral Percentage for Employees who are Nonhighly
                         Compensated Employees; and




                                     -37-
 
<PAGE>   43


                 (7)     The determination and treatment of the Elective
                         Deferrals and Actual Deferral Percentage of any
                         Employee shall satisfy such other requirements as may
                         be prescribed by the Secretary of Treasury.

        4.9      Distribution of Excess Deferrals.  "Excess Deferrals" means
excess deferrals as defined under Code section 402(g).  Notwithstanding any
other provision of the Plan, the Excess Deferral, if any, of each Employee with
respect to a calendar year plus any income and minus any loss allocable thereto
shall be distributed no later than April 15 of the following calendar year to
each Employee who claims an Excess Deferral for the preceding calendar year.
Excess Deferrals shall be treated as Annual Additions under the Plan.

The Employee's claim shall be in writing; shall be submitted to the Company no
later than March 1; shall specify the Employee's Excess Deferral for the
preceding calendar year; and shall be accompanied by the Employee's written
statement that if such amount is not distributed, such Excess Deferral, when
added to amounts deferred under other plans or arrangements described in Code
section 401(k), 408(k), or 403(b), exceeds the limit imposed on the Employee by
Code section 402(g) for the year in which the deferral occurred.

Notwithstanding the preceding paragraph, the Employer may notify the Plan on
behalf of the individual of Excess Deferrals to the extent that the individual
has Excess Deferrals for the calendar year calculated by taking into account
only elective deferrals under this Plan and other plans of the Company and any
Affiliated Company.

The Excess Deferral distributed to an Employee with respect to a calendar year
shall be adjusted for any income or loss thereon for such calendar year and for
the period between the end of such calendar year and the date of distribution.
The income or loss allocable to such calendar year shall be determined by



                                     -38-

 
<PAGE>   44


multiplying the income or loss for such calendar year allocable to the
Employee's Salary Reduction Account by a fraction, the numerator of which is
the Excess Deferral of the Employee for such calendar year and the denominator
of which is the Employee's Salary Reduction Account balance on the last day of
such calendar year.  The income or loss allocable to the period between the end
of such calendar year and the date of distribution shall be equal to 10 percent
of the income or loss allocable to the Excess Deferral for the preceding
calendar year multiplied by the number of calendar months that have elapsed
from the end of the preceding calendar year to the date of distribution.  A
distribution occurring on or before the fifteenth day of the month shall be
treated as having been made on the last day of the preceding month and a
distribution occurring after such fifteenth day shall be treated as having been
made on the first day of the following month.

In the event that an Employee's Salary Reduction allotments are distributed to
such Employee under this section 4.9, any Employer contributions attributable
thereto plus any income and minus any loss allocable thereto shall be
forfeited.

    4.10         Distribution or Recharacterization of Excess Contributions.
        (a)      Determination of Excess Contributions.  "Excess Contributions"
                 means, with respect to any Plan Year, the excess of--
                 (1)     the aggregate amount of Elective Deferrals actually
                         paid over to the Trust on behalf of Highly Compensated
                         Employees for such Plan Year, over
                 (2)     the maximum amount of such Elective Deferrals
                         permitted under the limitations of section 4.8(b),
                         determined by reducing Elective Deferrals as follows:
                         (A)      First, the Actual Deferral Percentage (as
                                  defined in section 2.1(b)) of the Highly



                                     -39-

 
<PAGE>   45


                                  Compensated Employee with the highest Actual
                                  Deferral Percentage is reduced to the extent
                                  necessary to satisfy the test described in
                                  section 4.8(b) or to cause such percentage to
                                  equal the Actual Deferral Percentage of the
                                  Highly Compensated Employee with the next
                                  highest Actual Deferral Percentage.
                         (B)      Second, this process is repeated until the
                                  test described in section 4.8(b) is satisfied.
                 Excess Contributions shall be treated as Annual Additions
                 under the Plan.

                 For purposes of this section 4.10, to the extent permitted by
                 the Code, the Excess Contributions shall be reduced by the
                 amount of any Excess Deferrals included in such Excess
                 Contributions and distributed to the Employee pursuant to
                 section 4.9.
        (b)      Distribution or Recharacterization.  Notwithstanding any other
                 provision of the Plan, either--
                 (1)     Excess Contributions with respect to a calendar year
                         plus any income and minus any loss allocable thereto
                         shall be distributed no later than the last day of the
                         following calendar year to Employees on whose behalf
                         such Excess Contributions were made for the preceding
                         calendar year; or
                 (2)     at the election of the Employee and to the extent
                         permitted by the Code, the Excess Contributions shall
                         be treated as distributed to the Employee and then
                         contributed by the Employee to the Plan as a Voluntary
                         Deduction allotment.
        (c)      Adjustment for Income and Loss.  The Excess Contributions to
                 be distributed to an Employee with respect to a calendar year
                 shall be adjusted for any income or loss thereon for such
                 calendar year and for the period between the end of such
                 calendar year and





                                    -40-
<PAGE>   46


                 the date of distribution.  The income or loss allocable to
                 such calendar year shall be determined by multiplying the
                 income or loss for such calendar year allocable to the
                 Employee's Salary Reduction Account by a fraction, the
                 numerator of which is the Excess Contributions for such
                 calendar year and the denominator of which is the Employee's
                 Salary Reduction Account balance on the last day of such
                 calendar year.  The income or loss allocable to the period
                 between the end of such calendar year and the date of
                 distribution shall be equal to 10 percent of the income or
                 loss allocable to the Excess Contributions for the preceding
                 calendar year multiplied by the number of calendar months that
                 have elapsed from the end of the preceding calendar year to
                 the date of distribution.  A distribution occurring on or
                 before the fifteenth day of the month shall be treated as
                 having been made on the last day of the preceding month and a
                 distribution occurring after such fifteenth day shall be
                 treated as having been made on the first day of the following
                 month.

                 In the event that an Employee's Salary Reduction allotments
                 are distributed to such Employee under this section 4.10, any
                 Employer contributions attributable thereto plus any income
                 and minus any loss allocable thereto shall be forfeited.

    4.11         Statutory (Code Section 415) Limitations on Allocations to
Accounts.  Notwithstanding any other provision of the Plan, contributions under
the Plan shall be subject to the limitations set forth in Code section 415,
which are incorporated herein by reference.  For purposes of applying such
limitations to contributions under the Plan, the rules set forth in this
section 4.11 shall be applicable.





 

                                    -41-
<PAGE>   47


        (a)      Annual Addition.  The term "Annual Addition" means the amount
                 allocated to a Participant's account during any calendar year
                 that constitutes--
                 (1)     Employer contributions;
                 (2)     Employee contributions;
                 (3)     forfeitures; and
                 (4)     amounts described in Code sections 415(l)(1) and
                         419A(d)(2).
                 The compensation limitation referred to in Code section
                 415(c)(1)(B) shall not apply to--
                 (A)     any contribution for medical benefits (within the
                         meaning of Code section 419A(f)(2)) after separation
                         from service which is otherwise treated as an Annual
                         Addition, or
                 (B)     any amount otherwise treated as an Annual Addition
                 under Code section 415(l)(1).  The Annual Addition for any
                 calendar year before 1987 shall not be recomputed to treat all
                 Employee contributions as an Annual Addition.
        (b)      Combined-Plan Limits.  In the case of an individual who was a
                 Participant in the Plan on December 31, 1986, an amount shall
                 be subtracted from the numerator of the defined contribution
                 fraction (not exceeding such numerator) as prescribed by the
                 Secretary of Treasury so that the sum of the defined benefit
                 plan fraction and defined contribution plan fraction does not
                 exceed 1.0 as of such date.

                 Code section 415 shall be applied in such manner as to
                 maximize the permissible contributions and benefits thereunder
                 and, in determining the permissible amount of contributions
                 under the Plan, any grandfathering provisions heretofore or
                 hereafter adopted pursuant to Code section 415 shall be
                 applicable.  For purposes of applying the limitations set
                 forth in Code section 415(e), the Michigan Consolidated Gas
                 Company





 

                                    -42-
<PAGE>   48


                 Retirement Plan For Employees Covered By Collective Bargaining
                 Agreement shall be the primary plan and any required
                 reductions shall be made in the Annual Additions to this Plan.
        (c)      Reduction of Annual Additions.
                 (1)     If the limitations of Code section 415 would be
                         exceeded as a result of a reasonable error in
                         estimating a Participant's compensation or on account
                         of such other limited facts and circumstances as the
                         Commissioner of Internal Revenue finds justify the
                         application of the rules hereinafter set forth, the
                         Annual Additions to the Participant's account which
                         exceed the applicable limitation shall be returned to
                         the Participant to the extent of all or any portion of
                         any Voluntary Deduction allotments which were made by
                         him pursuant to Article IV.  Any net earnings and
                         gains allocable to such allotments for the period
                         between the date of such allotment and the date
                         returned shall also be repaid to the Participant but
                         such return of net earnings and gains will not be
                         deemed a further reduction of any excess Annual
                         Additions.
                 (2)     If the Participant made no Voluntary Deduction
                         allotments or if, after returning all or part of such
                         allotments in accordance with the previous paragraph,
                         his Annual Additions still exceed the limitations of
                         Code section 415, then such excess shall be returned
                         to the Participant to the extent of all or any portion
                         of any Salary Reduction allotments made on behalf of
                         such Participant, together with any net earnings and
                         gains on such allotments as hereinabove described.
                 (3)     If, after returning all or any portion of Voluntary
                         Deduction and Salary Reduction allotments of a
                         Participant in accordance with the preceding
                         paragraphs, his Annual Additions still





                                    -43-
<PAGE>   49


                         exceed the limitations of Code section 415, such
                         portion of the Employer contributions under section
                         4.2 made on behalf of the Participant as must be
                         removed to meet the limitations shall be allocated and
                         reallocated to other Participants' Investment Plan
                         Accounts as contributions by the Employer.
                 (4)     If, after reallocating all or any portion of Employer
                         contributions under section 4.2, a Participant's
                         Annual Additions still exceed the limitation of Code
                         section 415, such portion of the Employer
                         contributions under section 4.3(a) made on behalf of
                         the Participant and shares of MCN Stock allocated to
                         his ESOP Account under section 13.4(d) as must be
                         removed to meet the limitations shall be allocated and
                         reallocated to other Participant's ESOP Accounts as
                         contributions by the Employer.
                 (5)     If, as a result of the allocation of forfeitures, a
                         reasonable error in estimating a Participant's
                         Compensation, or under other limited facts and
                         circumstances which the Commissioner of the Internal
                         Revenue Service finds justify the availability of the
                         following rules, any amount cannot be allocated during
                         the Plan Year in accordance with the foregoing
                         procedure without exceeding the applicable limitations
                         for one or more Participants, any remaining amount
                         shall be held unallocated in a special suspense
                         account to be allocated to Participants in the
                         succeeding Plan Year or Plan Years; provided, however,
                         that (A) no Employer contributions and no Voluntary
                         Deduction allotments shall be made in such succeeding
                         Plan Year or Plan Years until such special suspense
                         account is exhausted by allocations and reallocations;
                         (B) no investment gains (or losses) or other income
                         shall be





                                    -44-
<PAGE>   50


                         allocated to the special suspense account; and (C) the
                         amounts in the special suspense account shall be
                         allocated as soon as possible without violating the
                         limitations of this section 4.11.





 









                                    -45-
<PAGE>   51


                        Article V.  Vesting in Accounts

        5.1      Employee Salary Reduction Accounts, Employee Post-1986
Voluntary Deduction Account, and Employee Pre-1987 Voluntary Deduction Account.
The Employee Salary Reduction Account, the Employee Post-1986 Voluntary
Deduction Account, and the Employee Pre-1987 Voluntary Deduction Account of
each Participant shall be fully vested and nonforfeitable at all times.

        5.2      Employer Salary Reduction Account, Employer Voluntary
Deduction Account, and ESOP Account.
        (a)      In General.  A Participant shall have a vested and
                 nonforfeitable interest in his Employer Salary Reduction
                 Account, Employer Voluntary Reduction Account, and ESOP
                 Account after he has completed at least five Years of Service.
                 Prior to that time he shall have no vested interest in such
                 accounts.
        (b)      Accelerated Vesting.  Notwithstanding section 5.2(a) above, a
                 Participant shall be fully vested and have a nonforfeitable
                 interest in his entire Employer Salary Reduction Account,
                 Employer Voluntary Deduction Account, and ESOP Account if--
                 (1)     while still an Employee, he attains age 65;
                 (2)     while still an Employee, he dies or suffers a total
                         and permanent disability as defined in section 2.1(l);
                         or
                 (3)     while he is an Employee, contributions to the Plan are
                         completely discontinued or the Plan is terminated, or
                         the Plan is partially terminated and such Participant
                         is affected by such partial termination.





 



                                    -46-
<PAGE>   52


                       Article VI.  Investment Provisions

        6.1      Investment of Contributions and Allotments.  Employer
contributions under sections 4.2, 4.3, and 4.4 and Employee allotments shall be
invested in accordance with the following provisions:
        (a)      The Employer contributions made pursuant to section 4.3(a) and
                 (c) shall be invested in the MCN Stock fund, which fund is
                 described in Article VII.
        (b)      Each Participant shall, by written direction to the Company in
                 the form prescribed by the Company, direct that the Employer
                 contributions made pursuant to section 4.2 and Employee
                 allotments, including those made as a Salary Reduction, be
                 invested in such funds offered by the Trustee as are selected
                 by the Company.
Employee allotments, including those made as a Salary Reduction, and the
portion of Employer contributions referenced in section 6.1(b) above, need not
be invested in the same fund.  A Participant shall direct the manner in which
the total of such allotments and such Employer contributions referenced in
section 6.1(b) above shall be divided, equally or otherwise, among the funds.
With respect to any Employee who is a Participant on April 1, 1989 and who has
not filed a new election form to direct Employer contributions in accordance
with this section 6.1, Employer contributions under section 4.3(a) and (c)
shall automatically be directed to the MCN Stock fund and Employer
contributions under section 4.2 shall automatically be directed to the Fixed
Income fund.

        6.2      Change of Investment Direction.  Any investment direction
given by a Participant under section 6.1 shall be deemed to be a continuing
direction until changed by the Participant.  A Participant may change any such
direction in accordance with such procedures as the Company may from time to
time provide and apply in a nondiscriminatory manner.





 




                                    -47-
<PAGE>   53


        6.3      Transfers Between Investment Funds.  A Participant may direct
that all or any part of the value of his interest in any investment fund be
transferred to one or more of the other funds except that a Participant may not
transfer any amount from the MCN Stock fund to the extent that the balance
remaining in such fund immediately after the transfer would be less than the
value of his ESOP Account.  Notwithstanding the foregoing, no transfers may be
made to the Primark Corporation Stock fund by a Participant.

A transfer of all or any part of the value of a Participant's interest in the
Fixed Income fund may from time to time be restricted by the terms of
agreements which govern the investment of assets in such fund, in which event
the Company shall give notice of such restrictions to the Participants.

Prior to September 1, 1991, transfers between funds shall be effected only as
of the first day of any Accounting Period upon written directions to the
Company in the form prescribed by the Company given at least 20 days prior to
the effective date of such transfer.  Prior to September 1, 1991, if a
Participant shall direct the transfer of all or any part of the value of his
interest in a fund, the Participant shall not be allowed to direct transfers to
such fund for a period of one year from the date of such transfer.

Prior to April 30, 1991, the procedures set forth above were equally applicable
to the Primark Corporation Stock fund.  After that date, such fund ceased to
exist.





 




                                    -48-
<PAGE>   54


                         Article VII.  Investment Funds

        7.1      Investment Funds.  The Trustee shall establish, operate, and
maintain the following funds exclusively for the collective investment and
reinvestment of monies directed by the Company to be invested in such funds on
behalf of Participants:
        (a)      MCN Stock Fund.  A MCN Stock fund which shall be invested
                 solely in the common stock of MCN Corporation.
        (b)      Fixed Income Fund.  A Fixed Income fund which shall be
                 invested, except as hereinafter provided, in accounts or,
                 effective as of December 18, 1992, in marketable fixed income
                 securities or accounts maintained by financial institutions
                 which provide for fixed or variable rates of interest for
                 specified periods of time.  The terms of such agreements and
                 the selection of such institutions shall be determined by the
                 Company.  Investment advisors for marketable fixed income
                 securities may use fixed income futures and options to reduce
                 the effect of market volatility.
        (c)      Primark Corporation Stock Fund.  Until April 30, 1991, a
                 Primark Corporation Stock Fund to be invested in accordance
                 with the terms of this paragraph (e).  Until April 12, 1991,
                 the assets of the fund were and are to be invested solely in
                 Primark Corporation Stock.  As soon as practicable after April
                 12, 1991, the shares of Primark Corporation Stock in the fund
                 shall be sold and the proceeds of such sales shall be invested
                 solely in any short-term fixed income fund described in
                 section 8.1.  As of May 1, 1991 (or, if the sale of all shares
                 of Primark Corporation Stock is not completed by April 30,
                 1991, then June 1, 1991), the assets of the fund shall be
                 transferred to the MCN Stock Fund and the Primark Corporation
                 Stock Fund shall cease to exist.  Each Participant shall be
                 entitled to direct the transfer of all or any portion of the
                 amounts so





 



                                    -49-
<PAGE>   55


                 transferred to the MCN Stock Fund on his or her behalf to any
                 other fund or funds in accordance with, and subject to the
                 limitations of section 7.3.
        (d)      Other Funds.  Such other funds offered by the Trustee as the
                 Company may select.
Notwithstanding the foregoing, the Trustee or the investment manager, as the
case may be, shall invest such portion of the assets of the funds as the
Company may deem necessary or appropriate to facilitate the administration of
such funds in any short-term fixed income fund as may be established under any
common, commingled, or collective trust for employee benefit plans established
and maintained by the Trustee.

        7.2      Management of Investment Funds.  Except as otherwise provided
in this Article VII, each fund shall be under the exclusive management and
control of the Trustee; the ownership of the assets and investments of the
funds shall be in the Trustee as such; and the Trustee shall have in respect of
any and all assets of the funds the same powers as if it were absolute owner
thereof.

        7.3      Voting of MCN Stock.
        (a)      Instructions from Participants.  The Trustee shall vote, in
                 person or by proxy, shares of MCN Stock held by the Trustee in
                 the MCN Stock fund in accordance with instructions obtained
                 from Participants.

                 Each Participant shall be entitled to give voting instructions
                 with respect to the number of shares of such respective stock
                 which bears the same ratio to the total number of shares held
                 by the Trustee on the record date as the number of shares
                 allocated to the respective stock fund account of such
                 Participant as of the Valuation Date preceding such record
                 date bears to the total number of shares allocated to the
                 respective stock fund accounts of all Participants as of such










                                    -50-
<PAGE>   56


                 Valuation Date, excluding shares allocated to the accounts of
                 persons whose accounts have been distributed prior to such
                 record date.

                 Written notice of any meeting of stockholders of MCN
                 Corporation and a request for voting instructions shall be
                 given by the Company or the Trustee, at such time and in such
                 manner as the Company shall determine, to each Participant
                 entitled to give instructions for the voting of stock at such
                 meeting.

                 Shares with respect to which no voting instructions are
                 received from Participants and unallocated shares of the ESOP
                 shall be voted by the Trustee in the same proportion as shares
                 for which voting instructions are received from Participants.
                 The Trustee shall combine and vote fractional shares to the
                 extent possible to reflect the voting instructions of
                 Participants.
        (b)      Confidentiality.  The instructions received by the Trustee
                 from Participants shall be held by the Trustee in strict
                 confidence and shall not be divulged or released to any
                 person, including officers or employees of the Company or any
                 Affiliated Company.

        7.4      Tender Offers.
        (a)      Rights of Participants.  Notwithstanding any other provisions
                 of this instrument, in the event an offer is made generally to
                 the shareholders of MCN Corporation to transfer all or a
                 portion of the common stock of MCN Corporation in return for
                 valuable consideration including, but not limited to, offers
                 regulated by section 14(D) of the Securities Exchange Act of
                 1934, as amended, each Participant owning a beneficial
                 interest in the MCN Stock fund shall have the sole and
                 exclusive right to decide if the common stock representing his
                 interest in such fund shall be tendered.  Each Participant
                 shall have the right, to





 




                                    -51-
<PAGE>   57


                 the extent the terms of the tender offer so permit, to direct
                 the withdrawal of such shares from tender.  A Participant
                 shall not be limited as to the number of instructions to
                 tender or withdraw from tender which he can give; provided,
                 however, the Participant shall not have the right to give
                 instructions to tender or withdraw from tender after a
                 reasonable time established by the Trustee pursuant to section
                 7.4(c) below.
        (b)      Duties of the Company.  Within a reasonable time after the
                 commencement of a tender offer, the Company shall provide to
                 each Participant having an ownership interest in the MCN Stock
                 fund--
                 (1)     the offer to purchase as distributed by the offeror to
                         the shareholders of MCN Corporation,
                 (2)     a statement of the shares representing his interest in
                         the MCN Stock fund as of the most recent information
                         available from the Company, and
                 (3)     directions as to the means by which a Participant can
                         give confidential instructions to the Trustee with
                         respect to the tender.  The Company shall establish
                         and pay for a means such as, but not limited to,
                         Datagram by which a Participant can expeditiously
                         deliver to the Trustee instructions with respect to
                         the tender.
        (c)      Duties of the Trustee.  The Trustee shall follow the
                 instructions of the Participants with respect to the tender
                 offer.  The Trustee shall not tender shares for which no
                 instructions are received.  Unallocated shares of MCN Stock of
                 the ESOP shall be tendered or exchanged by the Trustee in the
                 same proportion as the allocated shares for which the Trustee
                 has received written direction are tendered or exchanged,
                 subject to the terms of any loan or pledge agreement covering
                 such shares.  On the basis of its ability to comply with the





 



                                    -52-
<PAGE>   58


                 terms of the offer, the Trustee shall establish a reasonable
                 time after which it shall not accept the instructions of
                 Participants.
        (d)      Confidentiality.  The instructions received by the Trustee
                 from Participants shall be held by the Trustee in strict
                 confidence and shall not be divulged or released to any
                 person, including officers or employees of the Company or any
                 Affiliated Company.

        7.5      Named Fiduciary Status.  For purposes of sections 7.3 and 7.4,
each Participant is hereby designated a "named fiduciary" within the meaning of
ERISA section 403(a)(1) with respect to shares of MCN Stock as to which he is
entitled to make voting or tender offer decisions.

        7.6      Expenses of Funds.  Brokerage commissions, transfer taxes, and
other charges and expenses in connection with the purchase and sale of
securities for a fund shall be charged to the fund.  Any income and other taxes
payable with respect to a fund shall likewise be charged to the fund.

        7.7      Primark Corporation Stock.  The provisions of sections 7.3,
7.4, and 7.5 pertaining to MCN Stock shall also be applicable to Primark
Corporation Stock during the period of its existence.





 




                                    -53-
<PAGE>   59


                Article VIII.  Accounts and Records of the Plan

        8.1      Company to Maintain Accounts.  The Company shall maintain, or
cause to be maintained, for each Participant--
        (a)      an Investment Plan Account attributable to Voluntary Deduction
                 allotments and related Employer contributions under section
                 4.2, and
        (b)      a separate account attributable to Salary Reduction allotments
                 and related Employer contributions under section 4.2,
each of which shall be composed, to the extent required by the investment
directions of the particular Participant, of a MCN Stock fund account, a Fixed
Income fund account, and an account for each other applicable fund in which his
allotments and related contributions are invested.

The Company also shall maintain, or cause to be maintained, for each
Participant--
        (c)      an ESOP Account attributable to Employer contributions under
                 section 4.3(a) and (c), and
        (d)      shares of MCN Stock allocated to the Participant pursuant to
                 section 13.4(d),
each of which shall be composed of a MCN Stock fund account and, to the extent
diversification elections are made by the Participant under section 13.5, such
other accounts as the Company or its delegate deems necessary or appropriate in
giving effect to the diversification requirements of section 13.5.

The Company shall maintain, or cause to be maintained, all necessary records.

        8.2      Plan Accounting.  The interests of each Participant in the
funds shall be his proportionate share of the value of such funds as of any
Valuation Date.  The Participant's proportionate share may be determined under
any accounting method selected by the Company that allocates fairly, in the
opinion of the





 
                                    -54-
<PAGE>   60


Company, the investment gains and losses by or on behalf of each Participant to
the fund and that complies with the Code requirements of the Code and the
Regulations thereunder.  The value of Participants' fund accounts shall be
redetermined as of each Valuation Date.

        8.3      Valuation of Funds.  The value of a fund as of any Valuation
Date shall be the market value of all assets (including any uninvested cash)
held by the fund as determined by the Trustee reduced by the amount of any
accrued liabilities of the fund on such Valuation Date.  The Trustee's
determination of market value shall be binding and conclusive upon all parties.

        8.4      Valuation of Investment Plan Account.  The value of a
Participant's Investment Plan Account as of any Valuation Date shall be the sum
of the values of his MCN Stock fund account, Fixed Income fund account, and any
other of his fund accounts attributable to Salary Reductions, Voluntary
Deductions, and Employer Contributions under section 4.2.

        8.5      Valuation of ESOP Account.  The value of a Participant's ESOP
Account as of any Valuation Date shall be the sum of--
        (a)      the value of his MCN Stock fund account attributable to
                 Employer contributions on his behalf under section 4.3(a) and
                 (c) and shares of MCN Stock allocated to his ESOP Account
                 under section 13.4(d); and
        (b)      the sum of the values of his Fixed Income fund account and any
                 other of his fund accounts attributable to diversification
                 elections under section 13.5.

        8.6      Valuation of Plan Account.  The value of a Participant's Plan
Account as of any Valuation Date shall be the sum of the values of his MCN
Stock fund account, Fixed Income fund account, and any other investment fund
accounts maintained on his behalf under the Plan.





 



                                    -55-
<PAGE>   61


        8.7      Company to Furnish Annual Statements of Value of Plan
Accounts.  The Company shall, not less frequently than annually, distribute to
each Participant in the Plan a statement setting forth the Plan Account of such
Participant.  Such statement shall be deemed to have been accepted as correct
unless written notice of objections thereto is received by the Company or the
Employer within 30 days after the distribution of such statement to the
Participant.

        8.8      Trust Agreement.  A Trust has been established to fund
benefits under the Plan.  The Employers may, without further reference to or
action by any Employee or Participant, from time to time enter into further
agreements with the Trustee and make such amendments to such Trust Agreement or
such further agreements as they may deem necessary or desirable to carry out
the Plan, and may take such other steps and execute such other instruments as
the Employers may deem necessary or desirable to put the Plan into effect or to
carry it out.





 





                                    -56-
<PAGE>   62


               Article IX.  Distributions, Withdrawals, and Loans

        9.1      Distribution Upon Termination of Employment Entitling
Participant to Value of Plan Account.  Upon termination of a Participant's
employment with his Employer--
        (a)      due to retirement on his Normal Retirement Date, his Early
                 Retirement Date, or his Disability Retirement Date,
        (b)      by the death of the Participant,
        (c)      because of total and permanent disability or legally
                 established mental incompetency of the Participant not
                 qualifying the Participant for retirement pursuant to section
                 2.1(l), or
        (d)      under any circumstances after the Participant has satisfied
                 the Vesting Requirement,
the Company shall, subject to the provisions of section 9.7, direct the Trustee
to distribute to the Participant, or, in a proper case his designated
beneficiary or legal representative, the value of the Participant's Plan
Account as of the Valuation Date coincident with or next following the date of
termination of employment.

Notwithstanding the foregoing, the value of a Participant's Plan Account shall
become nonforfeitable as of the date on which the Participant attains his
sixty-fifth birthday, provided he is an Employee on that date.

        9.2      Distribution Upon Termination of Employment Under
Circumstances Resulting in Forfeiture of Employer Contributions.  Upon
termination of a Participant's employment under circumstances other than those
described in sections 9.1 and 9.7(c)(2), the Company shall, subject to the
provisions of section 9.7, direct the Trustee to distribute to the Participant
an amount equal to the value of the Participant's Employee Pre-1987 Voluntary
Deduction Account, Employee Post-1986 Voluntary Deduction Account, and Employee
Salary Reduction Account each of which shall be fully vested and nonforfeitable
at all times.  The





 




                                    -57-
<PAGE>   63


Participant's Employer Voluntary Deduction Account, Employer Salary Reduction
Account, and ESOP Account shall be forfeited and applied in reduction of the
next succeeding contribution which the Participant's Employer would otherwise
contribute to the Trust; provided, however, if such Participant is reemployed
prior to his incurring five consecutive Break in Service Years, then as of the
Valuation Date coincident with or next following his date of reemployment, the
Participant's Employer shall contribute on behalf of such Participant an amount
equal to the amount that was forfeited upon his termination of employment, and
such contribution shall be credited to the same accounts from which it was
forfeited, in the same amounts, except amounts that would otherwise be credited
to the Primark Corporation Stock fund shall be credited to the MCN Stock fund.
Such contributions shall not be taken into account in determining under section
4.11 the Annual Additions to such Participant's Savings Plan Account.

        9.3      Certain Distributions from Participant Accounts.
        (a)      In General.  Any Participant may, upon 20 days' written notice
                 to the Company in the form prescribed by the Company,
                 terminate his participation in the Plan as of any Valuation
                 Date.  Upon such termination, the Company shall direct the
                 Trustee to distribute to the Participant an amount equal to
                 the value of the Participant's Employee Pre-1987 Voluntary
                 Deduction Account and Employee Post-1986 Voluntary Deduction
                 Account.  Such a Participant shall continue to be considered a
                 Participant for all purposes of the Plan except for purposes
                 of Article IV (Contributions), but shall be ineligible to
                 again elect to make allotments under the Plan for a period of
                 12 full Accounting Periods from the date of termination of his
                 participation.





 




                                    -58-
<PAGE>   64


        (b)      Withdrawals After Age 59 1/2.
                 (1)     Prior to January 25, 1991, upon 20 days' written
                         notice to the Company in the form prescribed by the
                         Company, any Participant who has satisfied the Vesting
                         Requirement and attained age 59 1/2 may terminate his
                         participation in the Plan as of any Valuation Date.
                         Upon such termination, the Company shall direct the
                         Trustee to distribute to the Participant the value of
                         his Plan Account as of such Valuation Date and such
                         Participant shall be ineligible to again elect to make
                         allotments under the Plan for a period of 12 full
                         Accounting Periods from the date of termination of
                         participation.
                 (2)     Effective January 25, 1991, upon 20 days' written
                         notice to the Company in the form prescribed by the
                         Company, any Participant who has attained age 59 1/2
                         may make an election, not more frequently than--
                         (A)      prior to December 1, 1993, once in any
                                  12-month period, or
                         (B)      on or after December 1, 1993, once every
                                  calendar year,
                         to withdraw all or any portion of the vested amount of
                         his Plan Account as of any Valuation Date.  Upon such
                         withdrawal, the Company shall direct the Trustee to
                         distribute to the Participant as of such Valuation
                         Date the amount the Participant has elected to
                         withdraw.
        (c)      Limited Withdrawal in the Event of Hardship.  Effective
                 January 25, 1991, if a Participant incurs a financial hardship
                 as defined in section 9.6, he may limit the amount of a
                 distribution from his Voluntary Deduction Account under
                 section 9.3(a) to the amount necessary to satisfy the hardship
                 and to pay any taxes resulting from such distribution.





 



                                    -59-
<PAGE>   65


        9.4      In-Service Withdrawals--General.  At its discretion, the
Company may adopt rules limiting the number of withdrawals that may be made in
any Plan Year and prescribe a minimum amount that may be withdrawn.  All
requests for a withdrawal shall be submitted in a form prescribed by the
Company.  A Participant may not rescind a request for withdrawal which has been
submitted to the Company unless the Company consents.  A withdrawal shall be
distributed as soon as reasonably practicable after the withdrawal request is
received.

        9.5      Withdrawal of Voluntary Deduction Allotments.  Any Participant
who shall have actively participated in the Plan for 24 or more calendar months
(for purposes of this section 9.5 active participation means the Participant
shall have made allotments to the Plan in each month in which compensation was
available), may, upon 20 days' written notice to the Company, withdraw as of
any Valuation Date an amount not in excess of 100 percent of his Voluntary
Deduction allotments under the Plan; provided, however, that the amount
withdrawn shall in no event exceed the sum of the values of his Employee
Pre-1987 Voluntary Deduction Account and Employee Post-1986 Voluntary Deduction
Account invested in the MCN Stock fund, the Fixed Income fund, and any other
investment funds under the Plan as of such Valuation Date.  Successive
withdrawals may be made at intervals of not less than two full years provided
that the total amount withdrawn may never exceed the limitations prescribed in
the preceding sentence.

Withdrawals under this section 9.5 shall be from the MCN Stock fund, the Fixed
Income fund, or such other investment funds offered by the Trustee as the
Company shall make available for purposes of this section.  If the Participant
has an account in more than one fund, he shall specify in his written direction
to the Company the amount to be withdrawn from each fund.  The allotments in
all funds in the Employee Pre-1987 Voluntary Deduction Account must be
withdrawn before a withdrawal is permitted from a fund in the Employee
Post-1986 Voluntary





 



                                    -60-
<PAGE>   66


Deduction Account.  The amount of an in-service withdrawal from a specific fund
in a Voluntary Deduction Account shall not exceed the Employee's allotments in
such fund prior to the withdrawal.

        9.6      Hardship Withdrawal of Salary Reduction Allotments.  A
Participant may request, upon 20 days' written notice to the Company, a
withdrawal from his Salary Reduction Account if the withdrawal is necessary to
satisfy an immediate and heavy financial need of a Participant as defined
below.  The amount of such withdrawal shall be limited to the Participant's
Salary Reduction allotments or the total value of the Participant's Employee
Salary Reduction Account as of the latest Valuation Date for which information
is available, whichever is smaller.  Withdrawals under this section 9.6 shall
be from the MCN Stock fund, the Fixed Income fund, or such other investment
funds under the Plan as the Participant specifies in his written request for a
hardship withdrawal.

The determination of whether or not a distribution is necessary to satisfy an
immediate and heavy financial need and the amount required to be distributed to
meet the need shall be made by the Company.  All determinations regarding
financial need shall be made in accordance with written procedures established
by the Company and applied in a uniform and nondiscriminatory manner.  Such
written procedures shall specify the requirements for requesting and receiving
distributions on account of financial need, including the forms that must be
submitted and to whom the forms are to be submitted.  All determinations
regarding financial need must comply with applicable Regulations under the
Code.

For purposes of this section 9.6, a financial hardship withdrawal shall be
limited to the amount required to meet the need created by one of the following
situations:
        (a)      Expenses for medical care described in Code section 213(d)
                 previously incurred by the Participant, his





 



                                    -61-
<PAGE>   67


                 spouse, or any dependents of the Participant or necessary for
                 these persons to obtain medical care described in Code section
                 213(d).
        (b)      Costs directly related to the purchase (excluding mortgage
                 payments) of the principal residence for the Participant.
        (c)      Payment of tuition and related educational fees for the next
                 12 months of post-secondary education for the Participant, his
                 spouse, children, or dependents (as defined in Code section
                 152).
        (d)      The need to prevent the eviction of the Participant from his
                 principal residence or foreclosure on the mortgage on the
                 Participant's principal residence.
A distribution will be deemed necessary to satisfy an immediate and heavy
financial need of a Participant only if both of the following conditions are
met:
        (1)      The distribution is not in excess of the amount of the
                 immediate and heavy financial need of the Participant.
                 Effective January 1, 1993, this amount may be increased by the
                 lesser of the amount withheld from the distribution under Code
                 section 3405(c), as enacted by section 522(b) of the
                 Unemployment Compensation Amendments of 1992, Public Law No.
                 102-318, Stat. 290 or remaining Salary Reduction allotments or
                 total value of the Salary Reduction Account, if less, after
                 subtracting the amount of the immediate and heavy financial
                 need.
        (2)      The Participant has obtained all distributions, other than
                 hardship distributions, and all loans available under this
                 Plan and all other plans maintained by the Employer.
If a Participant receives a hardship distribution, (A) the Participant shall
not be entitled to make Salary Reduction allotments or Voluntary Deduction
allotments for a period of one year after the hardship distribution, and (B)
the Participant may not make Salary Reduction allotments for the Participant's
taxable year immediately following the taxable year of the





 


                                    -62-
<PAGE>   68


hardship distribution in excess of the amount specified in Code section 402(g)
for such taxable year less the amount of the Participant's Salary Reduction
allotments for the taxable year of the hardship distribution.

        9.7      Time of Distributions.
        (a)      In General.  Except as hereinafter provided and subject to the
                 provisions of section 9.9, distributions made pursuant to
                 section 9.1 or 9.7(c)(2) shall be made by the Trustee at the
                 direction of the Company on such date as the Company shall
                 determine after consultation with the Participant or his
                 beneficiary, but in no event later than March 1 of the
                 calendar year following termination of the Participant's
                 employment.

                 Except as hereinafter provided, all other distributions or
                 withdrawals under this Article IX shall be paid as soon as
                 reasonably practicable by the Trustee at the direction of the
                 Company after the applicable Valuation Date.  Notwithstanding
                 any other provision of the Plan--
                 (1)     if the vested portion of a Participant's Plan Account
                         exceeds $3,500, no distribution shall be made to such
                         Participant pursuant to section 9.1, 9.2, 9.7(c)(2),
                         or 9.9 prior to the date the Participant attains the
                         age of 65 without written consent of the Participant;
                         and
                 (2)     if a distribution to a Participant is deferred
                         pursuant to (1), the amount that would otherwise have
                         been distributed to such Participant shall be
                         invested--
                         (A)      prior to August 1, 1991, in the Fixed Income
                                  fund, and
                         (B)      on and after August 1, 1991, in the Fixed
                                  Income fund or any other investment fund
                                  under the Plan, as the Participant shall
                                  direct,





 





                                    -63-
<PAGE>   69


                         except that the ESOP Account of such Participant shall
                         continue to be invested in the MCN Stock fund, subject
                         to the diversification rules set forth in section
                         13.5.
                 As soon as practicable after the date of adoption of the
                 Second Amendment to the Plan, the Company shall direct the
                 Trustee to transfer from the Fixed Income fund to the MCN
                 Stock fund, on behalf of each former Participant who
                 terminated employment on or after April 1, 1989 and prior to
                 the date of adoption of the Second Amendment, and whose
                 distribution has been deferred, an amount equal to the sum of
                 (A) the amount required to purchase the number of shares of
                 MCN Stock credited to his or her ESOP Account immediately
                 prior to his or her termination of employment, plus (B) the
                 amount of dividends that would have been credited thereon from
                 April 1, 1989 to the date of such transfer.  Such amount shall
                 be credited to the ESOP Account of such former Participant.

                 A former Participant whose distribution has been deferred
                 pursuant to (1) above will not thereafter be eligible for
                 withdrawals under section 9.3 or 9.5 or loans under section
                 9.10 but shall continue to have the voting and tender offer
                 rights described sections 7.3 and 7.4 and to be treated as a
                 Participant for purposes of Article VIII.

                 A former Participant whose distribution has been deferred may
                 initiate a distribution upon 30 days' prior written notice to
                 the Company and shall receive an amount equal to the vested
                 portion of his Plan Account as of the Valuation Date next
                 following the expiration of such 30-day period, with such
                 amount to be distributed in a lump sum cash payment except
                 that--
                 (i)     amounts invested in the MCN Stock fund shall be
                         distributed in accordance with section 9.8,





 


                                    -64-
<PAGE>   70


                 (ii)    effective as of August 1, 1991, such former
                         Participant may upon 30 days' prior notice to the
                         Company receive a partial distribution rather than a
                         total distribution, of the vested portion of his
                         Account, but not more frequently than once in any
                         calendar year (prior to December 1, 1993, not more
                         frequently than once in any 12-month period), and
                (iii)    to the extent that such distribution comes from the
                         Fixed Income fund account, such distribution shall be
                         subject to the provisions of section 9.9.
                 Notwithstanding any other provision of this Plan, if a
                 Participant attains age 70 1/2 and still has a balance
                 allocated to his or her Plan Account, a distribution shall be
                 made under section 9.1 as if the Participant had terminated
                 employment in the month in which the Participant attains age
                 70 1/2.  Such distribution shall in no event be later than
                 April 1 of the calendar year following the year in which the
                 Participant attains age 70 1/2.  Distributions to such
                 Participant shall be made annually thereafter no later than
                 April 1 of each year and shall be equal to at least the
                 minimum amount required to be distributed by Code section
                 401(a)(9).  For purposes of this paragraph, the life
                 expectancy of the Participant and the Participant's spouse
                 shall be redetermined annually.
        (b)      Suspension of Participation.  If a Participant shall, prior to
                 termination of his employment, cease to meet the eligibility
                 requirements of the Plan, his allotments and Employer
                 contributions on his behalf shall be suspended during the
                 period of his ineligibility.  Subject to section 3.1,
                 distribution of such Participant's Plan Account shall be
                 deferred until termination of his employment with the Company
                 and any Affiliated Company.  If the provisions of section 3.3
                 relating to the transfer of a Participant's Plan Account to
                 the MichCon Savings and Stock Ownership Plan or its successor
                 are not applicable--










                                    -65-
 
<PAGE>   71


                 (1)     with respect to Participants who cease to meet the
                         eligibility requirements of the Plan prior to
                         January 1, 1987, the Company shall direct the Trustee
                         to distribute the value of the Participant's Plan
                         Account in accordance with section 9.1 whether or not
                         such termination of employment shall be under the
                         circumstances set forth in said section 9.1; and
                 (2)     with respect to Participants who cease to meet the
                         eligibility requirements of the Plan subsequent to
                         December 31, 1986, such distribution shall be in
                         accordance with section 9.1 or 9.3, whichever is
                         applicable.
        (c)      Transfer of Employment.
                 (1)     A transfer of employment from an Employer to an
                         Affiliated Company shall not be considered a
                         termination of employment.
                 (2)     If a Participant shall be transferred to the employ of
                         an Affiliated Company which has not elected to
                         participate in the Plan, distribution of such
                         Participant's Plan Account shall be deferred until the
                         date on which he is no longer in the employ of the
                         Company or any Affiliated Company, whereupon the
                         Company shall direct the Trustee to distribute the
                         value of the Participant's Plan Account in the manner
                         prescribed in section 9.1, subject to the provisions
                         of section 9.7, whether or not termination of
                         employment shall be under circumstances set forth in
                         said section 9.1.
        (d)      Special Rules Relating to Distributions in the Event of Death.
                 In the event that a Participant dies before a distribution of
                 his Plan Account, the Company shall direct the Trustee to
                 distribute the entire value of his Plan Account to his
                 beneficiary no later than March 1 of the calendar year
                 following the Participant's death, as provided in section 9.1.
                 In











                                    -66-
<PAGE>   72


                 the event of the death of the Participant after the
                 distribution of his Plan Account has begun, any remaining
                 balance in his Plan Account at the time of death will be
                 distributed at least as rapidly as under the method of
                 distribution in effect at the date of the Participant's death.

        9.8      Distributions of Stock.  In the case of distributions under
section 9.1, 9.2, 9.3(b), 9.7(a), or 9.7(c)(2), the value of the Participant's
MCN Stock and/or Primark Corporation Stock fund account(s), if any, shall be
paid in full shares of stock except that cash shall be distributed in lieu of
fractional shares; provided, however, that a Participant entitled to such a
distribution may elect to receive cash in lieu of MCN Stock and/or Primark
Corporation Stock.  Except in the case of an election to receive cash in lieu
of MCN Stock and/or Primark Corporation Stock--
        (a)      prior to August 1, 1991, the number of shares to be
                 distributed from such account shall be the quotient of the
                 value of such account as of the applicable Valuation Date
                 divided by the value assigned by the Trustee to a share of MCN
                 Stock or Primark Corporation stock for purposes of valuing the
                 fund as of such Valuation Date; and
        (b)      on and after August 1, 1991, the total number of shares
                 allocated to such account shall be distributed from such
                 account.
Any remaining value of such account and, subject to the provisions of section
9.9, the value of the Participant's accounts in other funds shall be
distributed in cash.  Any transfer taxes payable with respect to the
distribution of shares of stock shall be charged to the respective MCN Stock or
Primark Corporation Stock fund.  Distributions pursuant to section 9.3(a) and
withdrawals under sections 9.5 and 9.6 shall be paid entirely in cash.





 




                                    -67-
<PAGE>   73


        9.9      Distributions from Fixed Income Fund.
        (a)      Normal Form.  Notwithstanding any provision of the Plan, other
                 than the final paragraph of section 9.7(a), if a distribution
                 is to be made under section 9.1(a) or (c) and the Participant
                 has a Fixed Income fund account and at least one Hour of
                 Employment prior to May 31, 1988, then unless the Participant
                 or legal representative shall make an election in the manner
                 prescribed in section 9.9(b), the value of such account
                 (exclusive of the portion thereof attributable to
                 diversification elections under section 13.5) shall be
                 distributed by the purchase of a single premium annuity
                 contract providing for monthly payments during the
                 Participant's lifetime and, if the Participant is married on
                 the date payment of his benefit commences and his spouse shall
                 survive him, for monthly payments during the remainder of such
                 spouse's lifetime, each such payment to such spouse being
                 equal to one-half of the monthly payment received by the
                 Participant, commencing no later than March 1 of the calendar
                 year following the calendar year of the Participant's
                 termination of employment, and delivery of such contract to
                 the Participant within a reasonable time after the
                 Participant's termination of employment.

                 If a distribution is to be made under section 9.1(b) because
                 of a Participant's death and the Participant had a Fixed
                 Income fund account at the time of his death and at least one
                 Hour of Employment prior to May 31, 1988, then unless the
                 Participant had made or the Participant's spouse or
                 beneficiary, as the case may be, makes an election at the time
                 and in the manner prescribed in section 9.9(b), the value of
                 the Participant's Fixed Income fund account (exclusive of the
                 portion thereof attributable to diversification elections
                 under section 13.5) shall be distributed by purchase of a
                 single premium annuity contract providing





                                    -68-
<PAGE>   74


                 for monthly payments to the Participant's spouse, or, if the
                 Participant was not married on the day of his death, to his
                 beneficiary during such person's lifetime, commencing no later
                 than March 1 of the calendar year following the calendar year
                 of the Participant's death and delivery of such contract to
                 such person within a reasonable time after the date of
                 Participant's death.
        (b)      Election to Reject Normal Form.  Subject to the provisions of
                 this section 9.9(b), each Participant entitled to a
                 distribution under section 9.9(a) (or legal representative on
                 behalf of such a Participant) may, at any time during the
                 90-day period ending on the annuity starting date, elect to
                 have the value of the Participant's Fixed Income fund account
                 (exclusive of the portion thereof attributable to
                 diversification elections under section 13.5) distributed by
                 one or more of the methods set forth in section 9.9(c).

                 Within 30 days after a Participant provides written notice to
                 the Company of his intention to retire on his Early Retirement
                 Date, Normal Retirement Date, or Disability Retirement Date,
                 or within 30 days after the Company receives notice of a
                 Participant's death, or within five business days after
                 determining, pursuant to section 2.1(l), that a Participant is
                 totally and permanently disabled, or within five business days
                 after receiving notice of the legally established mental
                 incompetency of the Participant, if the Participant has a
                 Fixed Income fund account at such time, the Company shall
                 deliver to such Participant or his legal representative, by
                 mail or by personal delivery, written notice in nontechnical
                 language explaining the terms and conditions of the annuity
                 provided in section 9.9(a).








                                    -69-
<PAGE>   75


                 The notice shall explain the Participant's or legal
                 representative's right to elect an optional form of
                 distribution and that such election may be revoked by the
                 Participant or legal representative at any time prior to the
                 annuity starting date or, if a lump sum payment is elected,
                 prior to the first day on which all events have occurred which
                 entitle the Participant or legal representative to the lump
                 sum payment.

                 The notice shall explain that a married Participant may elect
                 a distribution pursuant to section 9.9(c) only if the spouse
                 consents in writing to such election.  Such written consent
                 shall acknowledge consent to the designated beneficiary and
                 the optional form of distribution, neither of which may be
                 changed thereafter without again obtaining written spousal
                 consent (or the consent of the spouse expressly permits
                 changes by the Participant without further consent by the
                 spouse).  Such written consent shall acknowledge the effect of
                 such election and shall be witnessed by a notary public or by
                 a representative of the Company who is designated to act in
                 such capacity by the Company.

                 If the Participant establishes to the satisfaction of the
                 Company that such written consent cannot be obtained because
                 his spouse cannot be located, the requirement of such written
                 consent shall be waived. Any election, change, or revocation
                 under this section 9.9(b) shall be effective when written
                 notice is delivered to the Company in a form approved by the
                 Company for this purpose, provided such election, change, or
                 revocation is delivered prior to the annuity starting date or,
                 if a lump sum payment is elected, prior to the first day on
                 which all events have occurred which entitle the Participant
                 or legal representative to the lump sum payment.  The notice





 


                                    -70-
<PAGE>   76


                 shall explain that an effective revocation shall result in the
                 benefit being provided as an annuity described in section
                 9.9(a).
        (c)      Optional Forms.  In addition to the form described in section
                 9.9(a), distribution of the value of a Participant's Fixed
                 Income fund account (exclusive of the portion thereof
                 attributable to diversification elections under section 13.5)
                 may be made either--
                 (1)     in a lump sum payment no later than March 1 of the
                         calendar year following the calendar year of the
                         Participant's termination of employment or death; or
                 (2)     by purchase of any form of single premium annuity
                         contract that satisfies Code section 401(a)(9) as may
                         from time to time be offered by the legal reserve life
                         insurance companies with which the Trustee has
                         agreements governing the investment of assets in the
                         Fixed Income fund and delivery of such contract to the
                         Participant or distributee within a reasonable time
                         after the Participant's termination of employment or
                         death.  Within five business days after the Company
                         receives an election pursuant to this provision, the
                         Company shall provide the same written notice provided
                         under section 9.9(b).  An election pursuant to this
                         provision shall be subject to the provisions of
                         section 9.9(b).

    9.10         Loans.  The Trustee is hereby authorized to establish a loan
program in accordance with this section 9.10.  Upon application of a party in
interest (as defined in ERISA section 3(14)) who is a Participant or
beneficiary under the Plan, the





 




                                    -71-
<PAGE>   77


Company shall direct the Trustee to make a cash loan to such Participant or
beneficiary, secured by 50 percent of the nonforfeitable value of the
Participant's Employee and Employer Salary Reduction and ESOP Accounts
determined as of the date the loan is made.  The loan program shall be
administered by the Company subject to the following conditions and such other
conditions that are consistent with Labor Regulation section 2550.408b-1 and
are from time to time set forth in a written document, delivered to
Participants and beneficiaries who are parties in interest (which document may
but need not be the Summary Plan Description), which provisions shall
constitute a part of the Plan and are hereby incorporated by reference:
        (a)      Effective October 18, 1989, the term of a loan shall not
                 extend beyond the earlier of four years or the date upon which
                 the Participant or beneficiary ceases to be a party in
                 interest; provided, however, that the four years shall be
                 changed to eight years where the proceeds of the loan are used
                 by the Participant or beneficiary to acquire the Participant's
                 principal residence.
        (b)      Effective October 18, 1989, a loan shall bear interest at a
                 reasonable rate which shall be based upon the prevailing
                 interest rate charged by persons in the business of lending
                 money on similar commercial loans under comparable
                 circumstances at the time that such loan is granted, as
                 determined by the Company and uniformly applied.
        (c)      Effective October 18, 1989, the amount of a loan (when added
                 to the balance of other outstanding loans) shall not exceed
                 the lesser of--
                 (1)     $50,000 reduced by the excess (if any) of--
                         (A)      the highest outstanding balance of loans from
                                  the Plan during the one-year period ending on
                                  the day before the date on which such loan
                                  was made, over
                         (B)      the outstanding balance of loans outstanding
                                  on the date such loan was made, or





 


                                    -72-
<PAGE>   78


                 (2)     50 percent of the nonforfeitable value of the
                         Participant's Employee and Employer Salary Reduction
                         and ESOP Accounts under the Plan which the Participant
                         would have been entitled to receive if the
                         Participant's employment had terminated on the date
                         such loan was made.
                 In no case shall a Participant be entitled to a loan under
                 this Plan if the amount of the proposed loan is less than
                 $500.
        (d)      A loan shall be evidenced by a promissory note.
        (e)      Payments of principal and interest shall be made by
                 approximately equal payments not less frequently than monthly
                 on a basis that would permit the loan to be fully amortized
                 over its term.  Effective October 18, 1989, loan payments
                 shall be made by payroll deductions for Participants in active
                 pay status.
        (f)      Appropriate disclosure shall be made pursuant to the Truth in
                 Lending Act to the extent applicable.
        (g)      Amounts of principal and interest received on a loan shall be
                 credited to the Participant's account and the outstanding loan
                 balance shall be considered an investment of the assets of the
                 account.  Payment of principal and interest shall be credited
                 to the investment funds in the same proportion as the amount
                 distributed from the funds from which the loan was granted to
                 the Participant, except amounts that would otherwise be
                 credited to the Primark Corporation Stock fund shall be
                 credited to the MCN Stock fund.
        (h)      The frequency of loans and the minimum amount for a loan shall
                 be determined through uniform rules prescribed by the Company
                 and at the sole discretion of the Company.
        (i)      All applications for a loan shall be submitted to the Company
                 on a form prescribed by the Company.  Distribution shall be
                 made as soon as reasonably practicable after the application
                 of the loan is received.





 

                                    -73-
<PAGE>   79


        (j)      If a Participant borrows from an account which is invested in
                 more than one fund, he shall instruct the Company as to the
                 funds from which the loan is to be applied; provided, however,
                 that no borrowing shall be applied from the MCN Stock fund
                 unless and until the Participant's ability to borrow from each
                 of the other funds has been exhausted.
        (k)      A married Participant may not borrow any amount from the Plan
                 unless his spouse executes a written consent as hereinafter
                 provided.  Such consent must be executed during the 90-day
                 period ending on the date on which the loan is made and shall
                 specifically provide that the spouse consents both to the loan
                 and to the use of the Participant's Salary Reduction and ESOP
                 Accounts as security for the loan.  The consent shall
                 acknowledge the effect of the use of the Participant's
                 accounts as security for the loan and shall be witnessed by a
                 notary public or a representative of the Company who is
                 designated to act in such capacity by the Company.
        (l)      In the event a Participant defaults on a loan, the entire
                 outstanding balance of and accrued interest on the loan shall
                 be due and payable.  The Trustee and/or Company may pursue
                 collection on such defaulted loan by any means generally
                 available to a creditor where a promissory note is in default,
                 or if the entire amount due is not paid by such Participant
                 following the default, the amount of such loan default shall
                 be charged against the "secured portion" of the Participant's
                 Plan Account and treated as a distribution with respect to
                 such Participant; provided, however, that such a charge
                 against a Participant's Plan Account shall not occur with
                 respect to funds in his Employee Salary Reduction Account at a
                 time so as to cause a violation of Code section
                 401(k)(2)(B)(i).





 



                                    -74-
<PAGE>   80






    9.11         Definition of Allotments and Employer Contributions. For the
purposes of this Article IX, a Participant's allotments shall include only
those allotments made either as a Voluntary Deduction or a Salary Reduction
which have not been previously withdrawn or distributed.

If a Participant has previously had a portion of his Plan Account forfeited
under section 9.2, the Employer contributions, exclusive of those made as a
Salary Reduction to the Plan on his behalf, shall include only such Employer
contributions made subsequent to such forfeiture.

    9.12         Spousal Consent to Payment.  Subject to section 9.7(a), the
spouse of a married Participant or former Participant shall be required to
consent in writing to any in-service withdrawal, loan, or distribution under
the Plan to the Participant or former Participant; provided, however, for
distributions on account of termination of employment, this sentence shall be
effective as of January 1, 1993.  The spouse's consent shall be in such form as
the Company may prescribe.

    9.13         Distributions Pursuant to a Qualified Domestic Relations
Order.  Upon receipt of a domestic relations order, the Company will notify the
involved Participant and any alternate payee that the order has been received
and explain the Plan's procedures for determining whether the order is a
qualified domestic relations order as defined in Code section 414(p).  After
determining that the order is a qualified domestic relations order, the Company
shall direct the Trustee to distribute or segregate the Participant's Account
as provided in the qualified domestic relations order.  If required by the
qualified domestic relations order, the Trustee shall make distribution prior
to the time that the Participant, whose account is subject to distribution,
could have received a distribution.





                                      -75-
<PAGE>   81






In a case of a dispute regarding the validity of a domestic relations order or
the amounts or identities of parties to be paid thereunder, the Company may
segregate the portion of the Participant's account in question, and may bring
an action in a court of competent jurisdiction to determine the proper amount
and/or recipient of benefits, or may submit such segregated amount to a court
of competent jurisdiction (through an interpleader action or otherwise) until
resolution of the matter.

Further, if the Company receives notice that a domestic relations order is
forthcoming, the Company may suspend payments from the Participant's Account or
may follow the procedures described in the preceding sentence, until resolution
of the matter.

       9.14      Direct Rollovers of Eligible Distributions.
        (a)      General.  This section applies to distributions made on or
                 after January 1, 1993.  Notwithstanding any provision of the
                 Plan to the contrary that would otherwise limit a
                 distributee's election under this section, a distributee may
                 elect, at the time and in the manner prescribed by the
                 Company, to have any portion of an eligible rollover
                 distribution paid directly to an eligible retirement plan
                 specified by the distributee in a direct rollover.
        (b)      Definitions.
                 (1)     Eligible rollover distribution.  An eligible rollover
                         distribution is any distribution of all or any portion
                         of the balance to the credit of the distributee,
                         except that an eligible rollover distribution does not
                         include: any distribution that is one of a series of
                         substantially equal periodic payments (not less
                         frequently than annually) made for the life (or life
                         expectancy) of the distributee or the joint lives (or
                         joint life expectancies) of the distributee and the
                         distributee's designated beneficiary, or for a





                                      -76-
<PAGE>   82






                         specified period of ten years or more; any
                         distribution to the extent such distribution is
                         required under Code section 401(a)(9); and the portion
                         of any distribution that is not includible in gross
                         income (determined without regard to the exclusion for
                         net unrealized appreciation with respect to employer
                         securities).
                 (2)     Eligible retirement plan.  An eligible retirement plan
                         is an individual retirement account described in Code
                         section 408(a), an individual retirement annuity
                         described in Code section 408(b), an annuity plan
                         described in Code section 403(a), or a qualified trust
                         described in Code section 401(a), that accepts the
                         distributee's eligible rollover distribution.
                         However, in the case of an eligible rollover
                         distribution to the surviving spouse, an eligible
                         retirement plan is an individual retirement account or
                         individual retirement annuity.
                 (3)     Distributee.  A distributee includes an Employee or
                         former Employee.  In addition, the Employee's or
                         former Employee's surviving spouse and the Employee's
                         or former Employee's spouse or former spouse who is
                         the alternate payee under a qualified domestic
                         relations order, as defined in Code section 414(p),
                         are distributees with regard to the interest of the
                         spouse or former spouse.
                 (4)     Direct rollover.  A direct rollover is a payment by
                         the Plan to the eligible retirement plan specified by
                         the distributee.
        (c)      Waiver of 30-Day Notice Period.  If a distribution is one to
                 which Code sections 401(a)(ll) and 417 do not apply, such
                 distribution may commence less than 30 days after the notice
                 required under section 1.411(a)-11(c) of the Income Tax
                 Regulations is given, provided that:
                 (1)     the Company clearly informs the Participant that the
                         Participant has a right to a period of at





                                      -77-
<PAGE>   83






                         least 30 days after receiving the notice to consider
                         the decision of whether or not to elect a distribution
                         (and, if applicable, a particular distribution
                         option), and
                 (2)     the Participant, after receiving the notice,
                         affirmatively elects a distribution.





        









                                    -78-
<PAGE>   84






                           Article X.  Administration

       10.1      Plan Administration and Interpretation.
        (a)      The Company shall be responsible for the administration of the
                 Plan.  The Company shall have all such powers as may be
                 necessary to carry out the provisions of the Plan and may from
                 time to time establish rules and procedures for the
                 administration of the Plan and the transaction of the Plan's
                 business.
        (b)      The Company shall have the exclusive right to make any finding
                 of fact necessary or appropriate for any purpose under the
                 Plan.  The Company shall have the maximum discretion permitted
                 by law to interpret and construe the terms of the Plan and to
                 resolve all issues arising under the Plan including, but not
                 limited to the authority to--
                 (1)     construe disputed or doubtful terms of the Plan;
                 (2)     determine the eligibility of an individual to
                         participate in the Plan;
                 (3)     determine the amount, if any, of benefits to which any
                         Participant, former Participant, beneficiary, or other
                         person may be entitled under the Plan;
                 (4)     determine the timing and manner of payment of
                         benefits; and
                 (5)     resolve all other issues arising under the Plan.
                 To the extent permitted by law, all findings of fact,
                 determinations, interpretations, and decisions of the Company
                 shall be conclusive and binding upon all persons having or
                 claiming to have any interest or right under the Plan.

                 The Employers shall, from time to time, on request of the
                 Company, furnish to the Company such data and information as
                 the Company shall require in the performance of its duties.
        (c)      The Company shall each month collect Employee allotments and
                 Employer contributions from each





                                      -79-
<PAGE>   85






                 Employer and shall deliver the amounts collected to the
                 Trustee, together with instructions concerning the portions of
                 such total amount to be invested in each fund.
        (d)      The Company shall direct the Trustee to make payments of
                 amounts to be distributed or withdrawn from the Trust under
                 Article IX and to make any transfers from one fund to another
                 directed by Participants under section 6.3.

       10.2      Notice to Employees.  All notices, reports, and statements
given, made, delivered, or transmitted to a Participant shall be deemed to have
been duly given, made, or transmitted when mailed with postage prepaid and
addressed to the Participant at the address last appearing on the books of the
Employer.  A Participant may record any change of his address from time to time
by written notice filed with the Employer.

       10.3      Notices to Employers.  Written directions, notices, and other
communications from Participants to the Employers shall be mailed by first
class mail with postage prepaid or delivered to such location as shall be
specified upon the forms prescribed by the Company for the giving of such
directions, notices, and other communications, and shall be deemed to have been
received by the addressee when received at such location.  Any other notice to
the Employers shall be addressed--
        (a)      If intended for the Company:
                         MichCon Investment and Stock Ownership Plan
                         c/o Michigan Consolidated Gas Company
                         500 Griswold Street
                         Detroit, Michigan 48226
        (b)      If intended for any other Employer, at its principal place of
                 business.

       10.4      Participants' Acceptance of the Provisions of the Plan.  Each
Participant at the time of becoming a Participant in the





                                      -80-
<PAGE>   86






Plan and as a condition of participation shall sign an instrument evidencing
the fact that he accepts and agrees to all provisions of the Plan.

    10.5         Audit of Plan Records.  The records of the Company and the
records of the Employers in respect of the Plan shall be examined annually by a
firm of independent public accountants appointed by the Company.  Such
accountants shall, on the basis of such examination, make such reports to the
Company and to the Employers as they may request.  The audited records of the
Company and the Employers shall be conclusive in respect of all matters
involved in the administration of the Plan.

    10.6         Claims Procedure.  If any Participant or distributee believes
he is entitled to benefits in an amount greater than those which he is
receiving or has received, he may file a claim with the Secretary of the
Company.  Such a claim shall be in writing and state the nature of the claim,
the facts supporting the claim, the amount claimed, and the address of the
claimant.

The Secretary of the Company shall review the claim and, within a reasonable
period of time after receipt of the claim, give written notice by registered or
certified mail to the claimant of his decision with respect to the claim.  Such
notice shall be written in a manner calculated to be understood by the claimant
and, if the claim is wholly or partially denied, set forth the specific reasons
for the denial, specific references to the pertinent Plan provisions on which
the denial is based, a description of any additional material or information
necessary for the claimant to perfect the claim, and an explanation of why such
material or information is necessary, and an explanation of the claim review
procedure under the Plan.

The Secretary shall also advise the claimant that he or his duly authorized
representative may request a review by the Company of the denial by filing with
the Company, within 65 days after notice of the denial has been received by the
claimant, a





                                      -81-
<PAGE>   87






written request for such review.  The claimant shall be informed that he may
have reasonable access to pertinent documents and submit comments in writing to
the Company within the same 65-day period.  If a request is so filed, review of
the denial shall be made by the Company and the claimant shall be given written
notice of the Company's final decision.  Such notice shall be provided within
60 days after receipt of such request.  Such notice shall include specific
reasons for the decision and specific references to the pertinent Plan
provisions on which the decision is based and shall be written in a manner
calculated to be understood by the claimant.

    10.7         Effect of a Mistake.  In the event of a mistake or
misstatement as to the eligibility, participation, or service of any
Participant, or the amount of payments made or to be made to a Participant or
beneficiary, the Company shall, if possible, adjust the Plan's records and
cause to be withheld or accelerated or otherwise make adjustment of such
amounts of payments as will in its sole judgment result in the Participant or
beneficiary receiving the proper amount of payments under the Plan.











                                      -82-
<PAGE>   88






                     Article XI.  Amendment and Termination

    11.1         Amendment.  The Company may at any time and from time to time
amend or modify the Plan by written instrument duly adopted by the Board of
Directors of the Company.  Any such amendment or modification shall become
effective on such date as the Company shall determine, may apply to
Participants in the Plan at the time thereof as well as future Participants,
but may not reduce the Plan Account of any Participant as of the date of
adoption of such amendment or modification.

    11.2         Withdrawal.  If an Employer shall withdraw from the Plan under
section 12.2, or if an Employer shall adopt an amendment to the Plan which
shall render impracticable the continued administration of the Plan as a joint
plan of the several Employers, the Company shall determine the portions of the
various funds held by the Trustee which are applicable to the Participants of
such Employer and shall direct the Trustee to segregate such portions in a
separate trust.  Such separate trust shall thereafter be held and administered
as a part of the separate plan of such Employer.  After such portions of the
funds have been segregated in a separate trust, no such Participant or any
distributee with respect to such Participant shall have any right to any
benefit under the Plan or any claim against the Trust.

    11.3         Termination.  Any Employer may at any time terminate its
participation in the Plan by resolution of its Board of Directors without
obtaining the consent of or giving notice to any Participant or collective
bargaining representative.  In the event of any such termination, the Company
shall determine the portions of the various funds held by the Trustee which are
applicable to the Participants of such Employer and shall direct the Trustee to
distribute such portions to such Participants ratably in proportion to the
values of their respective fund accounts; provided, however, amounts
attributable to a Participant's Elective Deferrals shall not be distributed on











                                      -83-
<PAGE>   89






account of such termination if the Employer, after such termination, maintains
a defined contribution plan (other than an employee stock ownership plan or a
simplified employee pension).  The portions of the MCN Stock fund and the
Primark Corporation Stock fund so distributed shall be distributed in kind
except that cash shall be distributed in lieu of fractional shares.  The
portions of the Fixed Income fund and other investment funds so distributed
shall be distributed in cash or in kind, or partly in cash and partly in kind,
as determined by the Company.

Upon termination or partial termination of the Plan by any Employer or upon the
complete discontinuance of contributions by any Employer, the benefits under
the Plan of all affected Participants employed or formerly employed by such
Employer shall become nonforfeitable.

    11.4         Allocation of Funds Between Employers.  The portion of a fund
applicable to Participants of a particular Employer shall be an amount which
bears the same ratio to the value of the fund which the aggregate value of the
fund accounts of Participants employed by such Employer bears to the total
value of the fund accounts of all Participants.

    11.5         Trust to be Applied Exclusively for Participants and Their
Beneficiaries.  Subject to section 13.3, any provision of the Plan to the
contrary notwithstanding, it shall be impossible for any part of the Trust to
be used for or diverted to any purpose not for the exclusive benefit of
Participants and their beneficiaries either by operation or termination of the
Plan, by power of amendment, or by other means.

Notwithstanding the preceding paragraph, if a contribution is made to the Trust
by an Employer by a mistake of fact, then such contribution shall be returned
to such Employer within one year after the payment of the contribution; and if
any part or all of a contribution is disallowed as a deduction under Code
section 404, then to the extent such contribution is disallowed as a











                                      -84-
<PAGE>   90






deduction it shall be returned to such Employer within one year after the
disallowance.  All Employer contributions are conditioned upon their
deductibility under Code section 404.























                                      -85-
<PAGE>   91






              Article XII.  Participation by Affiliated Companies

    12.1         Adoption of the Plan.  Any Affiliated Company may become a
participating Employer under the Plan by (a) taking such corporate action as
shall be necessary to adopt the Plan, and (b) executing and delivering such
instruments and taking such other action as may be necessary or desirable to
put the Plan into effect with respect to such Affiliated Company.

The Plan shall become effective with respect to each particular Affiliated
Company which becomes a participating Employer after January 1, 1993, as of a
date to be determined by the Board of Directors of such Employer after
complying with all legal requirements pertaining to the participation of such
Employer in the Plan.

    12.2         Withdrawal from the Plan.  Any Employer may withdraw from
participation in the Plan at any time by filing with the Company a duly
certified copy of a resolution of its Board of Directors to that effect and
giving notice of its intended withdrawal to the Company, the other Employers,
and the Trustee at least 30 days prior to the effective date of withdrawal.

    12.3         Company as Agent for Employers.  Each Employer named under
section 2.1(u), other than the Company, hereby appoints, and each other
corporation which shall become an Employer pursuant to section 12.1 or 13.7 by
so doing shall be deemed to have appointed the Company its agent to exercise on
its behalf all of the powers and authorities hereby conferred upon the
Employers by the terms of the Plan, including, but not by way of limitation,
the power to amend, restate, and terminate the Plan.  The authority of the
Company to act as agent shall continue unless and until the portion of the
Trust fund held for the benefit of Employees of the particular Employer and
their beneficiaries is set aside in a separate trust as provided in section
11.2.










                                      -86-
<PAGE>   92






             Article XIII.  Special Provisions Relating to the ESOP

    13.1         Establishment of ESOP.  The MichCon Employee Stock Ownership
Plan for Union Employees was originally established effective as of April 1,
1989.  Each Employer shall make contributions to the ESOP in accordance with
section 4.3 hereof and the assets of the ESOP shall be invested at all times
primarily in MCN Stock.  The Company from time to time may direct the Trustee
to incur debt in accordance with section 13.4 hereof to finance the acquisition
of MCN Stock.

    13.2         ESOP Account.  The Company shall establish an ESOP Account in
the name of each Participant to which there shall be credited or charged--
        (a)      the Employer contributions under section 4.3(a) and (c) hereof
                 made on behalf of such Participant;
        (b)      the shares allocated to the Participant pursuant to section
                 13.4(d) hereof; and
        (c)      the investment gains and losses on such amounts.
A Participant's ESOP Account shall be invested only in the MCN Stock fund,
except to the extent that monies diversified under section 13.5 may, at the
Participant's election, be directed to the Equities fund, the Senior Securities
fund, or the Fixed Income fund.

    13.3         Discrimination Testing.  For purposes of the limitations on
Salary Reduction allotments set forth in section 4.8 and the limitations on
Voluntary Deduction allotments and Employer contributions set forth in section
4.11, the ESOP and non-ESOP portions of the Plan shall be tested separately.
For purposes of such testing--
        (a)      the ESOP portion of the Plan shall mean Employer contributions
                 under section 4.3(a) made on behalf of the Participant and the
                 shares allocated to a Participant's ESOP Account pursuant to
                 section 13.4(d); and







                                      -87-
<PAGE>   93






        (b)      the non-ESOP portion of the Plan shall mean all Elective
                 Deferrals, Voluntary Deductions and Employer contributions
                 under section 4.2.

    13.4         Loans.
        (a)      Stock Acquired with Exempt Loan.  The Company may direct the
                 Trustee to incur a loan on behalf of the ESOP in a manner and
                 under conditions which will cause the loan to qualify as an
                 "exempt loan" within the meaning of Code section 4975(d)(3).
                 A loan shall be used primarily for the benefit of Participants
                 and their beneficiaries.  The proceeds of each such loan shall
                 be used, within a reasonable time after the loan is obtained,
                 only to purchase MCN Stock, to repay the loan, or to repay any
                 prior loan.

                 Any such loan shall provide for a reasonable rate of interest
                 and an ascertainable period of maturity, and shall be without
                 recourse against the Plan.  Any such loan shall be secured
                 solely by shares of MCN Stock acquired with the proceeds of
                 the loan and shares of MCN Stock that were used as collateral
                 on a prior loan which was repaid with the proceeds of the
                 current loan.

                 MCN Stock acquired with the proceeds of a loan, including
                 shares pledged as collateral, shall be placed in a Suspense
                 Account and released in accordance with subsection (b) below
                 as the loan is repaid as if all shares in the Suspense Account
                 were pledged.  MCN Stock released from the Suspense Account
                 shall be allocated in the manner described in subsection (d)
                 below.

                 No person entitled to payment under a loan made pursuant to
                 this section 13.4 shall have recourse against any assets of
                 the Plan other than the MCN Stock used as collateral for the
                 loan, Employer contributions











                                      -88-
<PAGE>   94






                 under section 4.3 that are available to meet obligations under
                 the loan, and earnings attributable to such collateral and the
                 investment of such contributions.  Employer contributions
                 under section 4.3(b) made with respect to any Plan Year during
                 which the loan remains unpaid, and earnings on such
                 contributions, shall be deemed available to meet obligations
                 under the loan, unless otherwise provided by the Employer at
                 the time such contributions are made.
        (b)      Release of Pledged Shares.  Any pledge of MCN Stock as
                 collateral under this section 13.4 shall provide for the
                 release of shares so pledged upon the payment of any portion
                 of the principal of the loan.  Shares so pledged shall be
                 released in the proportion that the principal paid on the loan
                 bears to the total principal amount of the loan, as provided
                 in Treasury Regulation 54.4975-7(b)(8)(ii).  The number of
                 shares of MCN Stock that shall be released with each principal
                 payment on the loan shall be equal to the number of shares of
                 MCN Stock held as collateral on the loan immediately prior to
                 the release multiplied by a fraction the numerator of which is
                 the amount of principal of the loan repaid on such date and
                 the denominator of which is the sum of the numerator plus the
                 remaining outstanding principal amount of the loan after
                 giving effect to the repayment of principal of the loan on
                 such date.  Each loan under this section 13.4 shall comply
                 with the requirements of Treasury Regulation
                 54.4975-7(b)(8)(ii).  If such a loan provides for monthly
                 principal payments, shares of MCN Stock shall be released
                 monthly.
        (c)      Repayment of Loan.  Payments of principal and interest on any
                 loan under this section 13.4 shall be made by the Trustee at
                 the direction of the Company solely from--












                                      -89-
<PAGE>   95






                 (1)     the proceeds of such loan, if any portion of such
                         proceeds are used for such purpose within a reasonable
                         period of time after the loan is obtained as provided
                         in section 13.4(a) above;
                 (2)     Employer contributions under section 4.3(b) available
                         to meet obligations under the loan;
                 (3)     earnings from the investment of such contributions;
                 (4)     earnings attributable to MCN Stock acquired with the
                         proceeds of such loan, whether allocated or
                         unallocated;
                 (5)     the earnings on other allocated shares of MCN Stock
                         held by the ESOP if the Internal Revenue Service, by
                         private letter ruling, advises the Company that the
                         use of such earnings to repay the loan will be
                         deductible under Code section 404(k)(2)(C) and will
                         not violate the requirements of Code section 4975; and
                 (6)     the proceeds of a subsequent loan made to repay the
                         loan.
                 The contributions and earnings available to pay a loan must be
                 accounted for separately by the Company until all loans under
                 this section 13.4 have been paid.  If dividends on MCN Stock
                 allocated to the ESOP Account of any Participant are used to
                 repay any loan, shares of MCN Stock with a fair market value
                 not less than the amount of such dividends shall be allocated
                 in accordance with section 4.3(c) to the ESOP Account of such
                 Participant prior to the end of the Plan Year during which
                 (but for the use of the dividends to repay the loan) such
                 dividend would have been allocated to the ESOP Account of such
                 Participant.
        (d)      Allocation of Released Shares.  Subject to the limitations in
                 section 4.11 on Annual Additions to a Participant's accounts,
                 shares of MCN Stock released from a Suspense Account described
                 in section 13.4(a) shall be allocated immediately to the ESOP
                 Accounts of











                                      -90-
<PAGE>   96






                 each Participant in the proportion that the contribution that
                 would be required to be made on behalf of such Participant
                 under section 4.3(a)(1) for the applicable period if no shares
                 were allocated under section 4.3(a)(2) during such period
                 bears to the total of all Employer contributions that would be
                 required under section 4.3(a)(1) hereof for the applicable
                 period if no shares were allocated under section 4.3(a)(2)
                 during such period.

    13.5         Diversification.  Any Participant or any former Participant
whose distribution has been deferred pursuant to section 9.7(a), who, in either
case, has completed at least ten years of participation in the Plan, and who
has attained the age of 55 is a "Qualified Participant".  Any Qualified
Participant shall have the right to make an election to direct the investment
of a portion of his ESOP Account.  Such a Participant may elect within 90 days
after the close of each Plan Year in the six plan-year period beginning with
the first Plan Year in which the individual becomes a Qualified Participant to
diversify 25 percent of his ESOP Account, less any amount to which a prior
election applies.  In the case of the last year to which an election applies,
50 percent shall be substituted for 25 percent.

The portion of a Qualified Participant's ESOP Account which is eligible for
diversification may be invested in the Fixed Income fund and/or any other
investment funds under the Plan, in any combination thereof.

    13.6         Put Option.  If MCN Stock becomes not readily tradable on an
established market, then any Participant who is otherwise entitled to a
distribution of his ESOP Account, shall have the right (hereinafter referred to
as "Put Option") to require that his Employer repurchase any MCN Stock
allocated to his ESOP Account under a fair valuation formula.  The Put Option
shall be exercisable only by written notice to the Participant's Employer
during the 60-day period immediately following the date of











                                      -91-
<PAGE>   97






distribution and if the Put Option is not exercised within such 60-day period,
then it can be exercised for an additional period of 60 days in the following
Plan Year.  The period during which the Put Option is exercisable shall not
include any time when a Participant is unable to exercise it because his
Employer is prohibited from honoring it by applicable federal or state law.
This Put Option shall be nonterminable within the meaning of Treasury
Regulation 54.4975-(11)(a)(ii).

The amount paid for MCN Stock under the Put Option shall be paid in
substantially equal periodic payments (not less frequently than annually) over
a period beginning not later than 30 days after the exercise of the Put Option
and not exceeding five years.  There shall be adequate security provided and
reasonable interest paid on the unpaid balance due under this section 13.6.

    13.7         Purchase of MCN Stock.  The ESOP may acquire shares of MCN
Stock on a national securities exchange, from the Company or any Affiliated
Company or otherwise; provided, however, that if any shares of MCN Stock are
purchased from the Company or any Affiliated Company, the price shall not
exceed an amount which constitutes adequate consideration (as defined in ERISA
section 3(18) and any Regulations thereunder) and such purchase shall satisfy
all other requirements of ERISA and the Code applicable to such purchases.
Except as provided in section 13.6 or as otherwise required by applicable law,
no shares of MCN Stock acquired by the ESOP shall be subject to a put, call, or
other option, or buy-sell or similar arrangement while held by and when
distributed from the Plan, whether or not any part of the Plan is then an ESOP.
The protection afforded to Participants in the preceding sentence is
nonterminable within the meaning of Treasury Regulation section
54.4975-(1)(a)(ii).










                                      -92-
<PAGE>   98






                          Article XIV.  Miscellaneous

    14.1         Beneficiary Designation.  Subject to the provisions of section
9.9 and this section 14.1, each Participant shall have the right to designate a
beneficiary or beneficiaries to receive any distribution to be made under
section 9.1 upon the death of such Participant, or, in the case of a
Participant who dies subsequent to termination of his employment but prior to
the distribution of the entire amount to which he is entitled under the Plan,
any undistributed balance to which such Participant would have been entitled.

In the event of the death of a Participant whose spouse survives him, the
beneficiary of the Participant shall be his surviving spouse unless such spouse
has consented in writing to the designation of another beneficiary or
beneficiaries.  Any such written consent shall acknowledge the effect of such
election and shall be witnessed by a notary public or by a representative of
the Company who is designated to act in such capacity by the Company.  In the
event a Participant dies without a surviving spouse, or, in the event the
surviving spouse of a Participant has executed the written consent hereinabove
described, any distributions to be made under section 9.1 upon the death of the
Participant shall be made to his designated beneficiary or beneficiaries.  If
the Participant establishes to the satisfaction of the Company or its
designated representative that such written consent cannot be obtained because
his spouse cannot be located, the requirement of such written consent shall be
waived.

If no beneficiary has been named by a Participant who dies without a surviving
spouse or if the beneficiary designated by such a Participant or by a
Participant whose surviving spouse has executed the written consent hereinabove
described has predeceased the Participant or such designated beneficiary has












                                      -93-
<PAGE>   99






died prior to complete disbursement of the Participant's Plan Account, the
value of his account, or the undistributed portion thereof, shall be paid by
the Trustee at the direction of the Company--
        (a)      to the surviving spouse of such deceased Participant, if any;
        (b)      if there shall be no surviving spouse, to the surviving
                 children of such deceased Participant, if any, in equal
                 shares;
        (c)      if there shall be no surviving spouse or surviving children,
                 to the executors or administrators of the estate of such
                 deceased Participant; or
        (d)      if no executor or administrator shall have been appointed for
                 the estate of such deceased Participant, to the person or
                 persons who would be entitled to the personal estate of such
                 deceased Participant under the laws of his state of domicile
                 if he had died leaving no will.
In the event that a Participant and his spouse die under circumstances such
that it is not clear whether the spouse survived the Participant, the
Participant shall be presumed to have survived the spouse.

    14.2         Incompetency.  Any distribution under this Plan which is
payable to a beneficiary who is a minor or to a Participant or beneficiary who,
in the opinion of the Company, is unable to manage his affairs by reason of
illness or mental incompetency, may be made to or for the benefit of any such
Participant or beneficiary in such of the following ways as the Company shall
direct:
        (a)      Directly to any such minor beneficiary, if, in the opinion of
                 the Company, he is able to manage his affairs;
        (b)      To the legal representative of any such Participant or
                 beneficiary; or
        (c)      To some near relative of any such Participant or beneficiary
                 to be used for the latter's benefit.












                                      -94-
<PAGE>   100






    14.3         Expenses.  Except as otherwise provided in the Plan, all costs
and expenses incurred in administering the Plan, including the expenses of the
Company, the fees and expenses of the Trustee, the fees of its counsel, and
other administrative expenses, shall be borne by the Employers in such
proportions as the Company shall determine to be equitable and proper having
regard to the nature of the particular expense.

    14.4         Nonassignability.  Except as may be required to comply with a
qualified domestic relations order (as defined in Code section 414(p)), it is a
condition of the Plan, and all rights of each Participant shall be subject
thereto, that no right or interest of any Participant in the Plan or in a Plan
Account shall be assignable or transferable in whole or in part, either
directly or by operation of law or otherwise, including, but not by way of
limitation, execution, levy, garnishment, attachment, pledge, or bankruptcy but
excluding devolution by death or mental incompetency, and no right or interest
of any Participant in the Plan or in his Plan Account shall be liable for, or
subject to, any obligation or liability of such Participant.

    14.5         Employment Noncontractual.  The Plan confers no right upon any
Employee to continue in employment.

    14.6         Merger or Consolidation with Another Plan.  A merger or
consolidation with, or transfer of assets or liabilities to, any other plan
shall not be effected unless the terms of such merger, consolidation, or
transfer are such that each Participant, distributee, beneficiary, or other
person entitled to receive benefits from the Plan would, if the Plan then
terminated, receive a benefit immediately after the merger, consolidation, or
transfer which is equal to or greater than the benefit such person would have
been entitled to receive immediately before the merger, consolidation, or
transfer if the Plan had then terminated.












                                      -95-
<PAGE>   101






If any other plan shall be merged into and become a part of this Plan, each
Participant or the person entitled to receive a benefit under such other plan
shall be entitled to receive a benefit under this Plan which is equal to the
benefit such person would have been entitled to receive had such other plan
terminated immediately before the merger.

    14.7         Continuance by a Successor.  In the event that any Employer
corporation shall be reorganized by way of merger, consolidation, transfer of
assets, or otherwise, so that another Affiliated Company shall succeed to all
or a portion of such Employer's business, such successor corporation, with the
consent of each other participating Employer, may be substituted for such
Employer under the Plan by adopting the Plan and becoming a party to the Trust
Agreement.  Employee allotments and Employer contributions shall be
automatically suspended from the effective date of any such reorganization
until the date upon which the substitution of such successor corporation for
the Employer under the Plan becomes effective.  If, within 90 days from the
effective date of any such reorganization, such successor corporation shall not
have become a party to the Plan, or, if the Employer shall adopt a plan of
complete liquidation other than in connection with a reorganization, the Plan
shall be automatically terminated with respect to Employees of such Employer as
of the close of business on the ninetieth day following the effective date of
such reorganization or as of the close of business on the date of adoption of
such plan of complete liquidation, as the case may be, and the Trustee shall
distribute the portion of the Trust applicable to Participants of such Employer
in the manner provided in section 11.3.











                                      -96-
<PAGE>   102






    14.8         Elimination of Certain Provisions.  Effective--
        (a)      as of May 1, 1991, all references to Primark Corporation Stock
                 and the Primark Corporation Stock fund shall be deleted from
                 the Plan; and
        (b)      as of January 1, 1993, all provisions that ceased to apply on
                 any date prior to January 1, 1993 shall be deleted from the
                 Plan.

                              * * * * * * * * * *














                                      -97-
<PAGE>   103






        IN WITNESS WHEREOF, Michigan Consolidated Gas Company has caused its
corporate name to be hereunto affixed by its duly authorized officers as of the
29th day of December, 1993.

                       MICHIGAN CONSOLIDATED GAS COMPANY


ATTEST:
                                        By /s/ Carol McCallion
                                           -------------------


By /s/ Douglas A. Green
   --------------------
     (Corporate Seal)















                                      -98-
<PAGE>   104

                         FIRST AMENDMENT TO THE
                 1989 AMENDMENT AND RESTATEMENT OF THE
              MICHCON INVESTMENT AND STOCK OWNERSHIP PLAN


        WHEREAS, Michigan Consolidated Gas Company (the "Company") has
previously established the MichCon Investment and Stock Ownership Plan
(the "Plan"), which was most recently amended and restated effective
January 1, 1989;

        WHEREAS, FURTHER, pursuant to Section 11.1 of the Plan, the Company has
reserved the right to amend the Plan from time to time;

        WHEREAS, FURTHER, in connection with the process by which the Company is
seeking a favorable determination letter from the Internal Revenue
Service regarding the 1989 Amendment and Restatement of the Plan, the
Internal Revenue Service has requested that certain provisions of the
Plan be amended, effective January 1, 1989.

        NOW, THEREFORE, the Plan is hereby amended as follows, effective January
1, 1989:

        1.      The following shall be added at the end of Section 2.1(j):

                        If as a result of the application of such rules, the
                adjusted $200,000/$150,000 limitation is exceeded, then
                the limitation shall be prorated among the affected
                individuals in proportion to each such individual's
                compensation as determined under this Section prior to
                the application of the limitation.

        2.      Section 2.1(o) shall be amended by the addition of the following
at the end thereto:

                        If as a result of the application of such rules, the
                adjusted $200,000/$150,000 limitation is exceeded, then
                the limitation shall be prorated among the affected
                individuals in proportion to each such individual's
                compensation as determined under this Section prior to
                the application of the limitation.

        3.      Section 3.2 shall be amended in its entirety as follows:

                        Section 3.2  Eligibility Upon Merger or Reemployment.
                Any Employee who is a Participant in any plan which is
                merged into this Plan shall become a Participant in this
                Plan immediately upon the effective date of the merger.
                Such an Employee shall be eligible to actively
                participate in this Plan in accordance with Section 3.4.

<PAGE>   105


                If a Participant's employment is terminated and he is
                thereafter reemployed before incurring a Break in
                Service Year, he shall be eligible again to actively
                participate in the Plan as of the date of his
                reemployment.  In the event such Participant does incur
                a Break in Service Year, he shall be eligible again to
                actively participate in this Plan retroactive to his
                date of reemployment after he has again satisfied the
                eligibility requirement of Section 3.1(a).

        4.      Section 4.11(a)(4) shall be amended in its entirety to read as
follows:

                        (4)     Amounts described in Code Sections 415(l)(2) and
                419(A)(d)(3).

        5.      Section 4.11(a)(B) shall be amended in its entirety to read as
follows:

                        (B)     Any amount otherwise treated as an Annual
                Addition under Code Section 415(l)(2).

        6.      Section 8.3 shall be amended through the addition of the
following:

                To the extent any Employer securities held by the Plan
                are not readily tradable on an established securities
                market, valuation of such securities shall be made by an
                independent appraiser who meets requirements similar to
                the requirements of the regulations prescribed under
                Code Section 170(a)(1).

        7.      Section 9.7(a)(1) of the Plan shall be amended in its entirety
to read as follows:

                        (1)     If the vested portion of a Participant's Plan
                Account has ever exceeded $3,500, no distribution shall
                be made to such Participant pursuant to Section 9.1,
                9.2, 9.7(c)(2), or 9.9 prior to the date the Participant
                attains the age of sixty-five (65) without written
                consent of the Participant; and

        8.      Section 9.7 of the Plan shall be amended through the addition of
a new subsection (e) thereto, which shall read as follows:

                        (e) Distribution hereunder must begin not later than the
                sixtieth (60th) day after the close of the Plan Year in
                which occurs the latest of (a) the Participant's
                termination of employment, (b) the Participant's
                attainment of age sixty-five (65), or (c) the tenth
                (10th) anniversary of the date the Participant first

                                  -2-

<PAGE>   106
                became a Participant, unless (1) the Participant elects
                a later date by submitting to the Company a written
                statement signed by the Participant which describes the
                benefit and the date on which payment of such benefit
                shall commence, so long as such election does not
                violate the incidental benefit rule prescribed by the
                Code; or (2) if the amount of the payment required to
                commence on the date determined hereinabove cannot be
                ascertained by such date, or if it is not possible to
                make such payment on such date because the Company has
                been unable to locate the Participant after making
                reasonable efforts to do so, a payment retroactive to
                such date may be made no later than sixty (60) days
                after the earliest date on which the amount of such
                payment can be ascertained under the Plan or the date on
                which the Participant is located, whichever is
                applicable.  For purposes of this subsection, the
                failure of a Participant to consent to a distribution
                shall be deemed an election to defer commencement of
                payment of any benefit sufficient to satisfy this
                section.

        9.      Section 9.8 of the Plan shall be amended through the addition of
the following language at the end thereof:

                        The distribution requirements of Code Section 409(o)
                shall be met by the Plan, to the extent applicable.

        10.     Section 9.9(A) of the Plan shall be amended in its entirety to
read as follows:

                        (a) Normal Form.  Notwithstanding any provision of the
                Plan, other than the final paragraph of section 9.7(a),
                if a distribution is to be made under section 9.1(a) or
                (c) and the Participant has a Fixed Income fund account
                and at least one Hour of Employment prior to May 31,
                1988, then unless the Participant or legal
                representative shall make an election in the manner
                prescribed in section 9.9(b), the value of such account
                (exclusive of the portion thereof attributable to
                diversification elections under section 13.5) shall be
                distributed by the purchase of an immediately payable
                single premium annuity contract providing for monthly
                payments during the Participant's lifetime and, if the
                Participant is married on the date payment of his
                benefit commences and his spouse shall survive him, for
                monthly payments during the remainder of such spouse's
                lifetime, each such payment to such spouse being equal
                to one-half of the monthly payment received by the
                Participant, commencing no later than March 1 of the
                calendar year following the calendar year of the

                                  -3-
<PAGE>   107

                Participant's termination of employment, and delivery of
                such contract to the Participant within a reasonable
                time after the Participant's termination of employment.


                        If a distribution is to be made under section 9.1(b)
                because of a Participant's death and the Participant had
                a Fixed Income fund account at the time of his death and
                at least one Hour of Employment prior to May 31, 1988,
                then unless the Participant had made or the
                Participant's spouse or beneficiary, as the case may be,
                makes an election at the time and in the manner
                prescribed in section 9.9(b), the value of the
                Participant's Fixed Income fund account (exclusive of
                the portion thereof attributable to diversification
                elections under section 13.5) shall be distributed by
                purchase of an immediately payable single premium
                annuity contract providing for monthly payments to the
                Participant's spouse, or, if the Participant was not
                married on the day of his death, to his beneficiary
                during such person's lifetime, commencing no later than
                March 1 of the calendar year following the calendar year
                of the Participant's death and delivery of such contract
                to such person within a reasonable time after the date
                of Participant's death.

        11.     The second paragraph of Section 9.9(B) shall be amended through
the addition of the following at the end thereof:

                        In all cases, such notice shall be provided no less than
                thirty (30) days and no more than ninety (90) days prior
                to the annuity starting date.


        12.     A new section 9.15 shall be added to the Plan which shall read
as follows:

                        Notwithstanding anything herein to the contrary, a
                Participant's Salary Reduction contributions shall not
                be distributed prior to the Employee's retirement,
                death, disability, termination of employment, or
                hardship, except that a distribution of such amounts may
                be made, in accordance with Code Section 401(k)(10), upon

                        (a) termination of the Plan without establishment of
                another defined contribution plan other than an employee
                stock ownership plan (as defined in Code Section 4975(e)
                or 409) or a simplified employee pension plan (as
                defined in Code Section 408(k));

                        (b) the disposition by MCN Corporation or the Company to
                an unrelated corporation of substantially all

                                  -4-

<PAGE>   108
                of the assets (as defined in Code Section 409(e)(2))
                used in the trade or business if the Company continues
                to maintain the Plan after the disposition, but only
                with respect to employees who continue employment with
                the corporation acquiring such assets; or

                        (c) the disposition by MCN Corporation or the Company to
                an unrelated entity of its interest in a subsidiary
                (within the meaning of Code Section 409(d)(3)) if the
                Company continues to maintain the Plan, but only with
                respect to employees who continue employment with such
                subsidiary.

        13.     Other than as provided herein, the Plan shall remain unchanged.


        IN WITNESS WHEREOF, this Amendment has been executed as of this _____
day of __________, 1994.

                                MICHIGAN CONSOLIDATED GAS COMPANY



                                By  /s/ SUSAN K. MCNISH
                                   ---------------------------------------

                                  Its  GENERAL COUNSEL & SECRETARY
                                     -------------------------------------




                                  -5-

<PAGE>   109

                            SECOND AMENDMENT TO THE
                     1989 AMENDMENT AND RESTATEMENT OF THE
                      INVESTMENT AND STOCK OWNERSHIP PLAN


        WHEREAS, Michigan Consolidated Gas Company (the "Company") has
previously established the MichCon Investment and Stock Ownership Plan (the
"Plan"), which was most recently restated effective January1, 1989;

        WHEREAS, FURTHER, pursuant to Section 11.1 of the Plan, the Company has
reserved the right to amend the Plan from time to time;

        NOW, THEREFORE, the Plan is hereby amended as follows, effective
January1, 1995, except as otherwise provided below:

        1.      The first paragraph of Section 2.1(o) is amended in its
entirety as follows:

                (o)      "Eligible Compensation" means the regular basic salary
        or wage paid to an Employee by the Employer before any payroll
        deduction for taxes or any other purpose, and before any Salary
        Reduction allotment or cafeteria plan election, but excluding merit,
        incentive and other similar payments made in the form of a lump sum,
        bonuses, awards, shift differentials, severance payments, differential
        payments made by reason of the Employee's entry into Military Service,
        all amounts paid for work in excess of 40 hours in any one week, all
        overtime or other premium paid for work in excess of a maximum number
        of hours in any one day, for work on holidays or for any other reason,
        payments for so-called fringe benefits such as Employer contributions
        to this Plan or any pension or retirement plan, increased wages or
        salary resulting from temporary promotion, upgrading or transfer, of
        whatever duration, to a higher paid job or classification, and any
        other premium, auxiliary, or special pay of any sort whatsoever.

        2.      Section 3.7 is amended by adding the following at the end
thereof: 

                Notwithstanding anything herein to the contrary, Hours of
        Employment shall be credited hereunder at all times in compliance with
        the requirements of the Family and Medical Leave Act.

        3.      Section 4.1(a) is amended in its entirety as follows, effective
March 1, 1995:

                (a)      Amount of Allotments.  Each Participant may make a
        regular allotment to the Plan.  Such allotment shall not be less than
        1 percent nor more than the amount determined as follows:





                                       1
<PAGE>   110


                (1)     A Participant represented by S.E.I.U. Local 80
        (Detroit), P.T.& S. and I.C.W.U. Local 799 (P.T.& S.) and, prior to
        March 1, 1995, I.C.W.U. Local 70, may make allotments up to a percentage
        of his Compensation Rate, in incremental percentages of 1 percent,
        determined as follows:

<TABLE>
<CAPTION>
        Period                                     Percentage
        ------                                     ----------
        <S>                                        <C>

        Prior to April 1, 1992                             10%

        April 1, 1992 - August 31, 1993                    14%

        September 1, 1993 - February 28, 1995              15%

        March 1, 1995 and later
        (for Highly Compensated Employees)                 15%

        March 1, 1995 and later
        (for Nonhighly Compensated Employees)              20%
</TABLE>

                (2)     A Participant represented by I.C.W.U. Local 132 and 799
        (Northern) and, on and after March1, 1995, I.C.W.U.  Local 70, may make
        allotments up to a percentage of his Compensation Rate, in incremental
        percentages of 1 percent, determined as follows:

<TABLE>
<CAPTION>
        Period                                     Percentage
        ------                                     ----------
        <S>                                        <C>

        Prior to January 1, 1990                            8%

        January 1, 1990 - August 31, 1992                  10%

        September 1, 1992 - August 31, 1995
        (except for I.C.W.U. Local 70)                     14%

        March 1, 1995 - August 31, 1995
        (for I.C.W.U. Local 70)                            15%

        September 1, 1995 and later
        (for Highly Compensated Employees)                 15%

        September 1, 1995 and later
        (for Nonhighly Compensated Employees)              20%
</TABLE>

         Allotments will be effected by Voluntary Deductions, Salary
         Reductions, or any combination thereof, as elected by the Participant. 
         The amount of such Voluntary





                                       2
<PAGE>   111

Deductions or Salary Reductions shall be transferred to the Trustee after each
pay period; provided, however, that a Participant's Salary Reduction allotments
(A) shall be limited as provided in section 4.8 and (B) shall not exceed a
percentage of the Participant's Compensation Rate determined as follows:

        (i)      In the case of Participants referred to in (1) above --

<TABLE>
<CAPTION>
        Period                                             Percentage
        ------                                             ----------
        <S>                                                <C>

        Prior to April 1, 1992                                      6%

        April 1, 1992 - August 31, 1993                             8%

        September 1, 1993                                           9%
</TABLE>

(ii)    In the case of Participants referred to in (2) above --

<TABLE>
<CAPTION>
        Period                                             Percentage
        ------                                             ----------
        <S>                                                <C>

        Prior to September 1, 1992                                  6%

        September 1, 1992 - June 30, 1995                           8%
        (February 28, 1995 for I.C.W.U. Local 70)

        July 1, 1995 (March 1, 1995 for
         I.C.W.U. Local 70) and later                               9%
</TABLE>

Notwithstanding the foregoing, the Company may, in its sole discretion, (1)
reduce the Salary Reduction allotments permitted by a group of Participants if,
in the opinion of the Company, it is advisable to do so in order to satisfy the
requirements of section 4.8 or 4.11; or (2) reduce the Voluntary Deduction
allotments permitted by a group of Participants if, in the opinion of the
Company, it is advisable to do so in order to satisfy the requirements of
section 4.11.

        4.      Subsection (d) of Section 4.2 is amended in its entirety,
effective September1, 1993:

                (d)      Effective September 1, 1993 through December 31, 1994
        for all Participants:





                                       3
<PAGE>   112


<TABLE>
<CAPTION>
                                                           Contribution
                 Years of Service                           Percentage 
                 ----------------                          ------------
                 <S>                                              <C>
                 1 through 3                                        2%
                 More than 3 through 7                              3%
                 More than 7 through 10                             4%
                 More than 10 through 25                            5%
                 More than 25                                       6%
</TABLE>

5.      Section 4.2 is amended by adding new subsections (e), (f) and (g),
which shall read as follows:

        (e)      Effective January 1, 1995 for all Participants:

<TABLE>
<CAPTION>
                                                           Contribution
                 Years of Service                           Percentage 
                 ----------------                          ------------
                 <S>                                              <C>
                 1 through 3                                        2%
                 More than 3 through 6                              3%
                 More than 6 through 10                             4%
                 More than 10 through 25                            5%
                 More than 25                                       6%
</TABLE>

        (f)      Effective July 1, 1995 for all Participants except
Participants described in subsection (g) below:

<TABLE>
<CAPTION>
                                                           Contribution
                 Years of Service                           Percentage 
                 ----------------                          ------------
                 <S>                                              <C>
                 1 through 3                                        2%
                 More than 3 through 6                              3%
                 More than 6 through 10                             4%
                 More than 10 through 23                            5%
                 More than 23                                       6%
</TABLE>

        (g)      For all Participants who became Eligible Employees on or after
July1, 1995, who are utility employees represented by I.C.W.U. Local 799
(Northern):





                                       4


<PAGE>   113

<TABLE>
<CAPTION>
                                                           Contribution
                 Years of Service                           Percentage 
                 ----------------                          ------------
                 <S>                                              <C>
                 0 through 4                                        0%
                 More than 4 through 6                              3%
                 More than 6 through 10                             4%
                 More than 10 through 23                            5%
                 More than 23                                       6%
</TABLE>

6.      A new subsection (e) is added to Section 4.3, which shall read as
follows:

        (e)      Longevity Contributions.  Effective (1) April1, 1995 (with
respect to Participants represented by S.E.I.U. Local 80 (Detroit and P.T. &
S.) and I.C.W.U. Local 799 (P.T. & S.)) or (2) September 1, 1995 (with respect
to Participants represented by I.C.W.U. Locals 70, 132 and 799 (Northern)),
within a reasonable time after such initial date and each April1 of each Plan
Year thereafter (in each case, the "Measurement Date"), each Employer shall
contribute to the ESOP Account of each of its participating Employees on active
payroll as of the Measurement Date who has at least 30 Years of Service as of
such Measurement Date, twenty-five (25) shares of MCN stock (or an equivalent
value determined by the Company in a nondiscriminatory manner, which may be
used to purchase MCN stock).

7.      The second paragraph of subsection 4.11(b) is amended in its entirety
as follows:

        Code section 415 shall be applied in such manner as to maximize the
permissible contributions and benefits thereunder and, in determining the
permissible amount of contributions under the Plan, any grandfathering
provisions heretofore or hereafter adopted pursuant to Code section 415 shall
be applicable.  For purposes of applying the limitations set forth in Code
section 415(e), this Plan shall be the primary plan and any required reductions
shall be made from the Michigan Consolidated Gas Company Retirement Plan for
Employees Covered by Collective Bargaining Agreements (or other applicable
defined benefit plan of the Employer).

8.      Subsection 6.1(a) is amended in its entirety as follows:

        (a)      The Employer contributions made pursuant to section 4.3(a),
(c), and (e) shall be invested in the MCN Stock Fund (through each
Participant's ESOP Account), which fund is described in Article VII.





                                       5
<PAGE>   114


9.      The last paragraph of Section 6.1 is amended in its entirety as
follows:

        Employee allotments, including those made as a Salary Reduction, and
the portion of Employer contributions referenced in section 6.1(b) above, need
not be invested in the same fund.  A Participant shall direct the manner in
which the total of such allotments and such Employer contributions referenced
in section 6.1(b) above shall be divided, equally or otherwise, among the
funds.  With respect to any Employee who is a Participant on April1, 1989 and
who has not filed a new election form to direct Employer contributions in
accordance with this section 6.1, Employer contributions under section 4.3(a),
(c) and (e) shall automatically be directed to the MCN Stock Fund (through each
Participant's ESOP Account) and Employer contributions under section 4.2 shall
automatically be directed to the Fixed Income Fund.

10.     Subsection 8.1(c) is amended in its entirety as follows:

        (c)      an ESOP Account attributable to Employer contributions under
section 4.3(a), (c) and (e), and

11.     Subsection 8.5(a) is amended in its entirety as follows:

        (a)      the value of his MCN Stock fund account attributable to
Employer contributions on his behalf under section 4.3(a), (c) and (e) and
shares of MCN Stock allocated to his ESOP Account under section 13.4(d); and

12.     Section 9.7(a)(ii) is amended in its entirety as follows:

        (ii)     such former Participant may upon 30 days' prior notice to the
Company receive a partial distribution rather than a total distribution, of the
vested portion of his Account, but not more frequently than (1) once in any
calendar year (for the period ending June 30, 1995 for any Participant
represented by I.C.W.U. Locals 70, 132 and 799 (Northern) (1) three times in
any calendar year (during the period beginning January1, 1995 and ending
June30, 1995 for any Participant represented by S.E.I.U. Local 80 (Detroit and
P.T. & S.) and I.C.W.U. Local 799 (P.T. & S.))) or (2) four times per year
(effective July1, 1995 for all Participants), and

13.     Section 13.2(a) is amended in its entirety as follows:

        (a)      the Employer contributions under section 4.3(a), (c) and (e)
hereof made on behalf of such Participant;

14.     Other than as provided herein, the Plan shall remain unchanged.





                                       6
                                        
<PAGE>   115



        IN WITNESS WHEREOF, this Amendment has been executed as of this  day of
December, 1995.

                                        MICHIGAN CONSOLIDATED GAS COMPANY



                                        By /s/  SUSAN K. MCNISH
                                          ------------------------------------

                                          Its  SECRETARY AND GENERAL COUNSEL
                                             ---------------------------------





                                       7
                                        
<PAGE>   116


                             THIRD AMENDMENT TO THE
                     1989 AMENDMENT AND RESTATEMENT OF THE
                  MICHCON INVESTMENT AND STOCK OWNERSHIP PLAN


        WHEREAS, Michigan Consolidated Gas Company (the "Company") has
previously established the MichCon Investment and Stock Ownership Plan (the
"Plan"), which was most recently restated effective January 1, 1989;

        WHEREAS, FURTHER, pursuant to Section 11.1 of the Plan, the Company has
reserved the right to amend the Plan from time to time;

        NOW, THEREFORE, the Plan is hereby amended as follows, effective
January 1, 1996 except as otherwise provided below:

1.      Section 2.1(ww) shall be amended in its entirety as follows:

        "Valuation Date" means each business day on which the New York Stock
        Exchange shall be open for business.

2.      Section 4.5(a) shall be clarified by adding the following at the end
thereof, effective January 1, 1995:

        Former Employees who are Participants and who receive an eligible
        rollover distribution from another plan sponsored by an
        Employer may make rollover contributions in accordance with
        this section.

3.      Section 9.10(g) shall be amended in its entirety as follows:

        (g) Amounts of principal and interest received on a loan shall be
        credited to the Participant's account and the outstanding loan  balance
        shall be considered an investment of the assets of the account. 
        Payment of principal and interest related to loans made from a
        Participant's ESOP Account shall be credited to such Participant's ESOP
        Account.  Payment of principal and interest related to loans made from
        a Participant's Investment Plan Account shall be credited to the
        Participant's Investment Plan Account and shall be invested in the
        investment funds in the same proportions as the investment election
        then in effect by the Participant under Article VI.


                                       1



<PAGE>   117


4.      A new Section 14.9 shall be added to the Plan, effective October 12, 
1996, which shall read as follows:

        14.9 USERRA Rights.  Notwithstanding any provision of the Plan to the
        contrary, contributions, benefits and service credit with respect to
        qualified military service will be provided in accordance       with
        Code Section 414(u), to the extent applicable.  Loan repayments will be
        suspended under this Plan as permitted under Code Section 414(u).


5.      A new Article  XV shall be added to the Plan, effective as of January 1,
1996 provided that a favorable private letter ruling in connection with this
addition is received from the Internal Revenue Service on or before January 31,
1997, and which is otherwise effective on the January 1 of the year in which
such favorable private letter ruling is received, which such Article XV shall
read as follows:

                     Article XV.  Redesignation of ESOP

        This Article XV designates that part of the non-ESOP portion of the     
        Plan which is invested in the MCN Stock Fund becomes part of the ESOP
        portion of the Plan.  This Article XV also sets forth certain
        provisions regarding the operation of the ESOP portion of the Plan,
        such provisions to supersede any contrary provisions of the Plan.

        Except as specifically provided in this Article XV, the provisions of
        this Article XV, including the redesignation of the ESOP portion        
        of the Plan described herein, shall not affect any beneficiary
        designations or any other applicable agreements, elections, or consents
        that Participants, spouses, or beneficiaries validly executed under the
        terms of the Plan before the execution date of the Plan amendment which
        first adopts this Article XV, and such designations, agreements,
        elections and consents shall continue to apply in the same manner as
        they did prior to such amendment.

        The ESOP, as set forth in this Article XV, is intended to meet with
        requirements of an employee stock ownership plan, as defined in Section
        4975(e)(7) of the Code and the accompanying regulations, and Section
        407(d)(6) of ERISA.  As provided below, the ESOP is designed to invest
        primarily in qualifying employer securities of MCN Corporation.

        15.1 REDESIGNATION OF ESOP PORTION OF PLAN.  Effective as of January 1,
        1996, the  ESOP portion of the Plan shall consist of the ESOP   Account
        of each Participant plus the remaining part of each Participant's Plan
        Account that is invested in the MCN Stock Fund. The put option
        provisions of Section 13.6 shall apply to the entire ESOP portion of
        the Plan.  However, only a Participant's ESOP Account shall be subject
        to the restrictions described in the first sentence of Section 6.3.


                                       2



<PAGE>   118


        15.2 ALLOCATION OF INVESTMENT PLAN ACCOUNT BALANCES TO ESOP PORTION OF
        PLAN.  On and after January 1, 1996, all amounts contributed,   
        transferred or designated as allocable to the Investment Plan Account
        of any Participant shall be treated as part of the ESOP portion of the
        Plan to the extent the Participant has directed the investment of such
        amounts in the MCN Stock Fund in accordance with Article VI of the
        Plan.

        15.3 DISTRIBUTION OF DIVIDENDS ON MCN STOCK.  At the direction of the
        Company exercised in its sole discretion, the Trustee will,     after
        dividends are paid on MCN Stock held in the Trust, but in no event
        later than 90 days following the end of the Plan Year in which such
        dividends are paid (to the extent such dividends are not used to make
        payment on an exempt loan as provided for in section 13.4(c) of the
        Plan), either (i) distribute to Participants such portion of the
        dividends attributable to the interests in MCN Stock held in their Plan
        Accounts (or, if  so determined by the Company, their ESOP Accounts) as
        described below or, (ii)  arrange to have such dividends distributed
        directly to Participants by the Employer, or (iii) arrange to have such
        dividends distributed to Participants by a dividend disbursement agent
        selected by the Company, which may be the Employer's payroll
        department.  In its sole discretion, the Company may direct the Trustee
        to have such dividends distributed only to Participants who elect to
        receive such dividend distributions in accordance with procedures
        established by the Company (which such procedures may apply to all
        Participants, solely to Participants described in (a) below, or solely
        to Participants not described in (a) below).  Further, in its sole
        discretion, the Company may establish procedures that would permit
        Participants to elect to have dividends distributed to them in a single
        sum rather than over periods that might otherwise be determined by the
        Company to correspond with Employer payroll practices.

                The distribution of dividends on MCN Stock held in a
        Participant's Plan Account (or, if so determined by the Company, a
        Participant's ESOP Account ) shall be in the following amounts:

                a.      Participants who have terminated employment with
                        the Employers and all other nonemployees with Plan      
                        Account balances (such as QDRO alternate payees and
                        beneficiaries of deceased Participants) shall receive
                        distributions of all of the dividends paid on the MCN
                        Stock held in their Plan Accounts (or, if so determined
                        by the Company, their ESOP Accounts), provided,
                        however, that the aggregate amount of such
                        distributions to each such Participant or other
                        individual shall not exceed $3,500 in any Plan Year
                        (unless the Company, in its sole discretion, uniformly
                        permits such Participants to elect to receive such
                        distributions without limitation).

                                       3


<PAGE>   119



                b.      Participants who are employees who
                        participate in the MCN Supplemental Savings Plan
                        shall receive distributions of all of the dividends
                        paid on the MCN Stock held in their Plan Accounts
                        (or, if so determined by the Company, their ESOP
                        Accounts).

                c.      Each other Participant not described in (a)
                        or (b) above shall receive distributions equal to
                        the amount of Additional Allotments that he or she
                        would be permitted to make under Section 15.4
                        below, subject to the limitations of Section 15.5
                        below, unless such Participant affirmatively elects
                        to receive a distribution of 100% of the dividends
                        paid on the MCN Stock held in his or her Plan
                        Account (or, if so determined by the Company, his
                        or her ESOP Account).

                For purposes of this Section 15.3, the ESOP portions of both
        the MichCon Savings and Stock Ownership Plan and the MichCon Investment
        and Stock Ownership Plan shall be considered in the aggregate for
        each Participant and the payment of dividend amounts on MCN Stock held
        in the Plan Accounts (or, if so determined by the Company, the ESOP
        Accounts) under both plans shall not exceed the limitations on
        distributions of dividends set forth in subsections (a) and (c) above.
        In this regard, the limitations under subsections (a) and (c) shall be
        allocated among the two plans for a Participant by multiplying such
        limitation by a percentage derived by dividing the total of ESOP
        portion under each plan by the total ESOP portions under both plans
        (or, if so determined by the Company, by dividing the total ESOP
        Account under each plan by the total ESOP Account under both plans).

        15.4 ADDITIONAL ALLOTMENTS.  All active Employee-Participants will be
        deemed to have elected to make additional Salary Reduction allotments
        similar to those elected under Section 4.1 ("Additional Allotments")
        for each calendar year unless they affirmatively elect (under
        procedures established by the Company) not to make such allotments at
        least 15 days prior to the scheduled commencement of any distributions
        under  Section 15.3 above (the "Election Date"). The amount of
        Additional Allotments deemed to be elected under this Section 15.4
        shall be equal to the amount of ESOP dividends distributed to the
        Participant under Section 15.3 above, but subject to applicable legal
        limitations, including but not limited to the restrictions of Code
        Sections 402(g) and 415.  Such restrictions shall be applied in the
        manner determined by the Company in its sole discretion .  The amount
        of Additional Allotments shall be calculated by the Company utilizing
        uniform methodologies and assumptions established by the Company in its
        sole discretion.


                                       4



<PAGE>   120


        15.5 PROVISIONS FOR FURTHER REDUCTION OF ADDITIONAL ALLOTMENTS.  A
        Participant's Additional Allotments shall be further reduced as 
        necessary below the level described in Section 15.4 above so as to
        limit Additional Allotments to an amount equal to or not exceeding:

                a.      The lesser of (i) the residual of a
                        Participant's gross wages less all deductions
                        other than Additional Allotments or (ii) the
                        maximum further reduction permitted under
                        applicable law.

                b.      Zero, in the event that the Participant
                        does not make allotments pursuant to Section 4.1
                        of the Plan at the time of any distribution of
                        dividends pursuant to Section 15.3 above.

                c.      Zero, in the event that the Participant's
                        Plan Account is invested in  less than one share
                        of MCN Stock immediately prior to the distribution
                        of dividends.

        15.6 EMPLOYER CONTRIBUTIONS. Additional Allotments shall not be subject
        to the limitations on Salary Reduction and Voluntary Deduction
        allotments described in Section 4.1.  In addition, Additional
        Allotments shall not be treated as Salary Reduction or Voluntary
        Deduction allotments under Section 4.1 for the purposes of determining
        Employer contributions under 4.2 and 4.3 of the Plan, and shall be
        disregarded for these purposes.




        IN WITNESS WHEREOF, this Amendment has been executed as of this 23rd  
day of December, 1996.

     
                                        MICHIGAN CONSOLIDATED GAS COMPANY



                                        By /s/ Susan K. McNish  
                                          --------------------------------------
                                          Its V.P., General Counsel & Secretary
                                             -----------------------------------



                                       5