<PAGE>
                                                                   Exhibit 10(f)




--------------------------------------------------------------------------------

                                LIMITED GUARANTY

                           Dated as of March 31, 2000

                                       of

                              MINNESOTA POWER, INC.




                     --------------------------------------

                                 Lease Financing
                              for ADESA Corporation
                             Auto Auction Facilities


--------------------------------------------------------------------------------


                                      -1-

<PAGE>

                                LIMITED GUARANTY

         THIS LIMITED GUARANTY, dated as of March 31, 2000 (this "GUARANTY"), is
made by MINNESOTA POWER,  INC., a Minnesota  corporation (the  "GUARANTOR"),  to
SUNTRUST BANK, a banking  corporation  duly organized and validly existing under
the laws of the State of Georgia (the "CREDIT  BANK"),  and ASSET  HOLDINGS III,
L.P., an Ohio limited partnership (the "LESSOR").  Capitalized terms used herein
and  not  defined  herein  shall  have  the  meanings  ascribed  to  them in the
Participation  Agreement  dated as of the date hereof  among the  Lessor,  ADESA
Corporation,  an  Indiana  corporation  (the  "LESSEE"),  the  Credit  Bank  and
Cornerstone Funding Corporation I, a Delaware corporation (the "ISSUER"), as the
same may be amended from time to time (the "PARTICIPATION AGREEMENT").

                                   WITNESSETH:

         WHEREAS, as contemplated by the Participation Agreement, the Lease, the
Reimbursement  Agreement,  the Borrower  Promissory Note and the other Operative
Documents,  at the request of the Lessee, (i) the Lessor has agreed to lease the
Leased  Property  to the  Lessee  and the  Lessee has agreed to lease the Leased
Property  from the Lessor  pursuant to the Lease,  (ii) the Issuer has agreed to
issue and sell its Floating Rate Notes, Series 2000A, in the aggregate principal
amount of $28,373,000  and lend the proceeds from the sale thereof to the Lessor
to  provide  refinancing  for  certain  indebtedness  incurred  by the Lessor in
connection  with its  acquisition  of the Leased  Property,  (iv) the Lessor has
agreed  to  invest  from  its  own  equity  resources  an  amount  equal  to the
Contribution  in the  principal  amount of  $877,515.46,  to pay  certain  costs
related to the  transactions  contemplated by the Operative  Documents,  (v) the
Credit Bank has agreed to issue the Letter of Credit to secure  repayment of the
Notes upon  compliance  with the other  terms and  conditions  of the  Operative
Documents,  and (vi) the Lessor  has in the  Reimbursement  Agreement  agreed to
reimburse the Credit Bank for Drawings under the Letter of Credit and to pay all
Letter of Credit Liabilities.

         WHEREAS,  as  security  for its  obligations  under  the  Reimbursement
Agreement,  the Lessor has,  INTER ALIA,  assigned  all of its right,  title and
interest in the Lease to Credit Bank  pursuant  to the  Assignment  of Lease and
Rents dated of even date herewith; and

         WHEREAS,  for the  purposes  of this  Guaranty,  the  term  "GUARANTEED
OBLIGATIONS"  means at any time, subject to the limitations set forth in Section
1 below, any or all of the following,  without  duplication:  (i) payment to the
Lessor and the Credit Bank of, and performance of, all of the obligations of the
Lessee  under  the  Lease,  the  Assignment  of Lease  and  Rents  and the other
Operative  Documents,  including  but not  limited  to the  payment of Rent (the
amount of which includes,  without limitation or duplication,  the amount of all
Drawings,  all Letter of Credit Fees and all Letter of Credit Liabilities),  the
payment of the Lease Balance and the payment of the Recourse  Deficiency Amount,
at the times and in the circumstances under which the payment of such amounts is
provided for in the Lease and the other Operative  Documents,  (iii) the payment
and performance of the obligations of the Lessee to pay the applicable  purchase
price and purchase the Leased  Property  pursuant to the  provisions of ARTICLES
XI,  XIV and XV of the  Lease,  and  (iv) the  payment  and  performance  of all
obligations  of the  Lessee  under  the  Participation  Agreement  and the

<PAGE>

other Operative  Documents,  all without  duplication and in accordance with the
respective  terms and provisions of the Lease, the  Participation  Agreement and
the other Operative Documents; and

         WHEREAS,  the Guarantor  intends this Guaranty to be an inducement  (i)
for the Credit  Bank to issue the Letter of Credit,  which the Credit Bank would
be unwilling to do if the  Guarantor  did not execute and deliver this  Guaranty
and (ii) for the  Lessor to invest  the  Contribution  and enter into the Lease,
which the Lessor would be unwilling to do if the  Guarantor  did not execute and
deliver this Guaranty.

         NOW,  THEREFORE,  in  consideration of the premises and intending to be
legally  bound by this  Guaranty,  the  Guarantor  hereby  agrees to be bound as
follows:

         1.  The Guarantor  hereby unconditionally guarantees to the Credit Bank
and the  Lessor  the due and  punctual  payment  and  performance  of all of the
Guaranteed Obligations,  and further unconditionally  guarantees and agrees with
the  Credit  Bank and the  Lessor  that all sums due or payable by the Lessee in
respect of the  Guaranteed  Obligations,  together with any other sums which may
become due and payable by the Lessee  pursuant to any  Operative  Document  with
respect to the Guaranteed  Obligations,  but only to the extent  provided in the
Operative Documents, whether the same shall accrue before or after the filing of
a proceeding  under the Bankruptcy Code, shall be promptly paid in full (a) when
due,  whether  at stated  maturity,  or on the  Lease  Termination  Date,  or by
acceleration or otherwise,  in accordance with the provisions of such Guaranteed
Obligations  and of the  Operative  Documents or (b) upon the  occurrence  of an
Event of Default hereunder.

         Notwithstanding  anything  to  the  contrary  herein  contained,  it is
expressly  understood  and agreed  that this  Guaranty  shall not  constitute  a
guaranty of an amount in excess of the Recourse  Deficiency  Amount in the event
that the Lessee shall (A) exercise the Remarketing Option in accordance with the
provisions  of SECTION  15.6 of the Lease,  (B)  timely  comply  with all of the
obligations  and satisfy  all of the  conditions  set forth in SECTION  15.6 (i)
through (xiii) of the Lease, including,  without limitation,  the timely payment
in full of the Recourse  Deficiency Amount pursuant to the provisions of SECTION
15.6(x) of the Lease and (C) return and  surrender  the Leased  Property  to the
Lessor or, if applicable, the independent purchaser thereof, pursuant to, and in
compliance with, the provisions of SECTION 15.8 of the Lease.

         This  Guaranty  shall  be  irrevocable,  and in  all  events  shall  be
continuing,  unconditional and absolute, and if for any reason any such sums, or
any part thereof,  shall not be paid promptly when due, the Guarantor  shall pay
the same to the Credit  Bank to and in  accordance  with the  provisions  of the
Guaranteed  Obligations and the Operative Documents,  regardless of any defenses
or rights of set-off or counterclaim, regardless of whether the Credit Bank, the
Lessor or any  successor  in  interest  of either of them,  shall have taken any
steps to enforce its or their rights against the Lessee, the Lessor or any other
Person,  to collect such sums, or any part thereof,  and regardless of any other
condition or  contingency.  The Guarantor also agrees to pay to the Credit Bank,
the Lessor and such  successors  in interest  such  further  amounts as shall be
sufficient  to cover the costs and  expense of  collecting  such  sums,  or part
thereof,  or of  otherwise  enforcing  this  Guaranty,  including,  in any case,
reasonable fees of their respective  attorneys for all services rendered in that
connection.

                                      -2-
<PAGE>

         If the  Guarantor  shall be  required by  Applicable  Law to deduct any
charges from or in respect of any sum payable  hereunder to the Credit Bank, (i)
the sum payable by the Guarantor  shall be increased as may be necessary so that
after  making  all  required  deductions  (including  deductions  applicable  to
additional sums payable under this paragraph) the Credit Bank receives an amount
equal to the sum it would have been  entitled to receive from the Lessee and the
Lessor, as the case may be, under the Operative Documents had no such deductions
been  made,  (ii) the  Guarantor  shall  make  such  deductions,  and  (iii) the
Guarantor shall pay the full amount deducted to the relevant taxation  authority
or other authority in accordance with Applicable Law.

         The obligations of the Guarantor  hereunder shall be unaffected by, and
shall remain in full force and effect in the event that,  a bankruptcy  court or
other  court of  competent  jurisdiction  shall at any time  determine  that the
transactions  represented by the Lease and the other Operative  Documents (i) do
not constitute true leasing  transactions,  (ii) shall be treated as a financing
or loan transaction or shall otherwise be recharacterized, or (iii) shall in any
respect be held to be unenforceable in accordance with their respective terms.

         2.  The Guarantor  hereby  unconditionally  (a) waives any  requirement
that the Credit  Bank  first  make  demand  upon,  or seek to  enforce  remedies
against,  any other  Person or any of the  collateral  or property of such other
Person  before  demanding  payment  from,  or seeking to enforce  this  Guaranty
against, the Guarantor;  (b) covenants that this Guaranty will not be discharged
except by complete  satisfaction by indefeasible  payment in cash in full of all
payment obligations of Guarantor contained in the Guaranteed  Obligations and in
the Operative Documents with respect to the Guaranteed  Obligations;  (c) agrees
that, to the extent  permitted by law, this Guaranty shall remain in full effect
without  regard to, and shall not be affected or  impaired  by, any  invalidity,
illegality,  irregularity  or  unenforceability  in  whole  or in  part  of  the
Guaranteed  Obligations,  any other Operative Document (and the Guarantor hereby
waives any defense relating to the enforceability of the Operative  Documents or
any  provision  contained  therein),  or any  limitation of the liability of the
Guarantor  thereunder,  or any  limitation  on the  method  or terms of  payment
thereunder  which  may now or  hereafter  be  caused or  imposed  in any  manner
whatsoever;  (d) waives diligence,  presentment and protest with respect to, and
any notice of default in, the payment of any amount at any time payable under or
in connection with the Guaranteed Obligations or any of the Operative Documents;
and (e) agrees  that each and every  right,  power and remedy  given  under this
Guaranty or any other Operative  Document shall be cumulative and not exclusive,
and be in addition to all other  rights,  powers and  remedies  now or hereafter
granted or otherwise existing.

         3.  Notwithstanding  any  payment or payments  made by the Guarantor
hereunder or any set-off or  application of funds of the Guarantor by the Credit
Bank, until all of the Guaranteed  Obligations have been  indefeasibly  paid and
performed in full,  the Guarantor  shall not (a) be entitled to be subrogated to
any of the rights of the Credit Bank against the Lessee, the Lessor or any other
guarantor or in any  collateral  security or guaranty or right of offset held by
the Credit  Bank for the  payment  of any sums due in respect of the  Guaranteed
Obligations,  or (b) seek any reimbursement or contribution from the Lessee, the
Lessor or any other guarantor in respect of any payment,  set-off or application
of funds made by the Guarantor hereunder.

         4.  The  obligations, undertakings and  conditions to be  performed or
observed by the Guarantor  under this Guaranty shall not be affected or impaired
by  reason  of the  happening  from

                                      -3-
<PAGE>
time to time of any of the following with respect to the Guaranteed  Obligations
and the other Operative Documents, all without notice to, or the further consent
of, the Guarantor:

             (a) the waiver by the  Lessor, the Credit  Bank or any other Person
         of  the  observance  or  performance  by  the  Guarantor  of any of the
         obligations,  undertakings  or  conditions  contained  in any  of  such
         Guaranteed Obligations or any of the Operative Documents, except to the
         extent of such waiver;

             (b) the waiver by the Lessor, the Credit Bank or any other Person,
         of the  observance or performance by the Lessor or the Lessee of any of
         the  obligations,  undertakings  or  conditions  contained  in any such
         Guaranteed Obligations or any of the Operative Documents;

             (c) the extension,  in whole or in part, of the time for payment of
         any amount owing or payable under any of the Guaranteed  Obligations or
         any  Operative  Document or of any other sums or  obligations  under or
         arising  out of or on  account  of the  Guaranteed  Obligations  or any
         Operative Document except to the extent of such extension;

             (d) the  modification  or  amendment   (whether  material  or
         otherwise) of any of the  obligations of the Lessor or the Lessee under
         or with  respect  to any of the  Guaranteed  Obligations  or any of the
         Operative Documents, or the modification or amendment (whether material
         or otherwise)  of any of the  obligations  of the  Guarantor  under any
         other Operative Document,  except to the extent of such modification or
         amendment;

             (e) the taking or the  omission of any of the  actions  referred to
         in  any  Guaranteed   Obligation  or  any  other   Operative   Document
         (including,  without limitation,  the giving of any consent referred to
         therein);

             (f) any failure, omission, delay or lack on the part of the Lessor,
         the Credit Bank, or any other Person to enforce, assert or exercise any
         right,  power or remedy conferred on the Lessor, the Credit Bank or any
         other  Person in any of  Operative  Documents  or with  respect  to the
         Guaranteed  Obligations  or any action on the part of the  Lessor,  the
         Credit Bank,  or any other Person  granting  indulgence or extension in
         any form;

             (g) the release or discharge of the Lessor, the Lessee, or any
         other Person from the  performance  or  observance  of any  obligation,
         undertaking  or condition to be performed by the Lessor,  the Lessee or
         any such Person under any Guaranteed  Obligation or any other Operative
         Document by operation of law;

             (h) the receipt and  acceptance by the Lessor, the Credit Bank,  or
         any other Person of notes,  checks or other instruments for the payment
         of money and extensions and renewals thereof;

             (i) any payment by the Lessee to the Credit Bank or the Lessor
         if such payment is held to constitute a preference under the bankruptcy
         laws, or if for any other reason Credit

                                      -4-
<PAGE>

         Bank or Lessor is  required  by a court of  competent  jurisdiction  to
         refund such payment to the Lessor, the Lessee or pay the amount thereof
         to any other party ;

             (j) any  action,  inaction  or  election  of  remedies  by the
         Lessor,  the  Credit  Bank or any other  Person  which  results  in any
         impairment or destruction of any  subrogation  rights of the Guarantor,
         or any rights of the Guarantor to proceed  against any other Person for
         reimbursement;

             (k) the surrender by the Lessor,  the Credit Bank or any other
         Person  of any  security  at any  time  held  for  the  performance  or
         observance  of any of the  agreements,  covenants,  terms or conditions
         contained  in the  Operative  Documents or affecting in any respect the
         Guaranteed Obligations;

             (l) any event or circumstance (other than payment) which might
         otherwise  constitute  a legal or  equitable  discharge or defense of a
         guarantor,  indemnitor or surety under the laws of the State of Ohio or
         any other jurisdiction;

             (m) any other circumstances whatsoever (with or without notice to
         or knowledge of the Guarantor) which constitute,  or might be construed
         to  constitute,  an equitable or legal  discharge of the Guarantor with
         respect  to its  obligations  hereunder  or under the  other  Operative
         Documents,  in  bankruptcy  or in any other  instance,  except based on
         payment or performance;

             (n) any change in  circumstances,  whether or not  foreseen or
         foreseeable,  whether or not  imputable to the  Guarantor or the Lessor
         and whether or not such change in  circumstances  shall or might in any
         manner and to any extent vary the risk of the Guarantor hereunder; or

             (o) any other cause, whether similar or dissimilar to the
         foregoing;

         5.  It being  the  intention  of the  Guarantor  that this Guaranty  be
absolute and  unconditional in any and all  circumstances and that this Guaranty
shall be discharged  only by the  indefeasible  payment in full of all sums with
respect to which this Guaranty relates.

         6.  Each of the following  shall constitute an event of default ("EVENT
OF  DEFAULT"),  whatever  the  reason  for such  event and  whether  it shall be
voluntary or  involuntary  or be effected by operation of law or pursuant to any
judgment  or  order  of any  court  or any  order,  rule  or  regulation  of any
governmental or non-governmental body:

             (a) An Event of Default as defined in ARTICLE XIII of the Lease.

             (b) Any  default by the  Guarantor in the payment of any amount due
                 hereunder  which shall remain unremedied for five days after
                 written notice to the Guarantor.

                                      -5-
<PAGE>

             (c) Any  representation  or  warranty  made  by the Guarantor under
         this Guaranty or any other agreement,  report,  certificate,  financial
         statement or other  instrument  referred to herein and furnished to the
         Credit Bank in connection  herewith shall prove incorrect or misleading
         in any material respect when made and shall remain  unremedied for five
         days after written notice to the Guarantor.

             (d) The  Guarantor   shall  default  in  the  performance  or
         observance  of any  agreement or covenant  contained  in this  Guaranty
         (other than a covenant or  agreement or default in the  performance  or
         observance  of  which  is  elsewhere  in this  Section  6  specifically
         addressed)  and such  default  shall  continue  for a period of 10 days
         after written notice to the Guarantor.

             (e) The filing by the Guarantor of a petition for the  appointment
         of a trustee with respect to itself or any of its property.

             (f) The making by the Guarantor of an assignment for the benefit of
         creditors.

             (g) The  commencement by  the Guarantor of a case  in bankruptcy or
         insolvency or for compromise, adjustment or other relief under the laws
         of the United States or of any state relating to the relief of debtors.

             (h) The  failure of the  Guarantor  to obtain  the  dismissal,
         within 60 days after service upon the  Guarantor of any case  commenced
         against  the  Guarantor  (i) for the  appointment  of a trustee for the
         Guarantor,  of any of its property or (ii) in  bankruptcy or insolvency
         or for  compromise,  adjustment  or other  relief under the laws of the
         United States or of any state relating to the relief of debtors.

             (i) The failure of the Guarantor to generally pay its debts as such
         debts become due.

             (j) The making, or the attempted making, by the Guarantor of a
         fraudulent  conveyance  within the  meaning of the  Uniform  Fraudulent
         Conveyances Act.

             (k) Any  "Event of  Default"  (as  defined  in any such  other
         Operative  Document)  under  any of the  Lease or any  other  Operative
         Document  (after  the  expiration  of all  applicable  cure and  notice
         periods) and such "Event of Default" shall continue for a period of ten
         (10) days after the Guarantor's  receipt of written notice thereof from
         the Credit Bank or the Lessor.

         7.  Notice of acceptance of this  Guaranty and notice of the execution
             and delivery of any other instrument  referred to in this Guaranty,
             are hereby waived by the Guarantor.

         8.  (a) If any  Event  of  Default  (other  than an  Event  of  Default
         specified  above in Section  6(e) through (h) hereof  inclusive)  shall
         have  occurred  and be  continuing,  the Credit  Bank may,  in its sole
         discretion  (i) require the Trustee to draw upon the full amount of the
         Letter of Credit then  available  to be drawn as provided in the Letter
         of

                                      -6-
<PAGE>

         Credit  and the  Indenture,  (ii)  declare  all  obligations  of the
         Guarantor  under  this  Guaranty  to be  immediately  due and  payable,
         whereupon  all  such  obligations  shall  become  immediately  due  and
         payable,  and (iii)  proceed  first and directly  against the Guarantor
         under this Guaranty without  proceeding  first or concurrently  against
         the Lessee,  the Lessor or any other guarantor,  without exhausting any
         other remedies it may have (including, without limitation, any remedies
         under the Reimbursement  Agreement or the other Operative Documents) or
         without resorting to any other security held by the Credit Bank.

             (b) If any Event of Default  specified  above in Section  6(e)
         through (h) hereof  inclusive  shall occur (i) all  obligations  of the
         Guarantor  under this  Guaranty  shall  immediately  and  automatically
         become due and payable,  without  notice of any kind,  all of which are
         hereby  expressly  waived,  and (ii) the Credit  Bank may,  in its sole
         discretion, (A) require the Trustee to draw upon the full amount of the
         Letter of Credit then  available  to be drawn as provided in the Letter
         of Credit and the Indenture, and (B) proceed first and directly against
         the  Guarantor  under  this  Guaranty   without   proceeding  first  or
         concurrently  against  the Lessee,  the Lessor or any other  guarantor,
         without  exhausting any other remedies it may have (including,  without
         limitation,  any remedies  under the  Reimbursement  Agreement or other
         Operative Documents) or without resorting to any other security held by
         the Credit Bank.

         9.  In the event any payment by the Lessee, the Lessor or the Guarantor
to the Credit Bank or the Lessor,  as the case may be, is held to  constitute  a
preference under the bankruptcy laws, or if for any other reason the Credit Bank
or the Lessor, as the case may be, is required to refund by a court of competent
jurisdiction  any such  payment or pay the amount  thereof to any other  Person,
such  payment to the Credit  Bank or the Lessor,  as the case may be,  shall not
constitute or effect a release of Guarantor  from any liability  hereunder,  but
this Guaranty shall continue to be effective or shall be reinstated, as the case
may be, to the extent of any such  payment,  as though such payment had not been
made in the first instance,  and Guarantor agrees to pay an amount equal to such
payment to the Credit Bank or the Lessor,  as the case may be. The provisions of
this paragraph shall survive the termination of this Guaranty.

         10. The Guarantor does hereby represent and warrant that:

             (a) It  is a  corporation  duly organized,  existing and in good
         standing under the laws of the jurisdiction of its organization; it has
         corporate  power to enter into and perform all  agreements  on its part
         herein contained; the execution,  delivery and performance by Guarantor
         of this  Guaranty  has been  authorized  by all  necessary  and  proper
         corporate  action;  the  execution  and  delivery by  Guarantor of this
         Guaranty  does  not,  and  its  performance  of the  agreements  herein
         contained  will not,  contravene  or  constitute  a  default  under any
         agreement,  indenture,  commitment,  provision  of  its  organizational
         documents, or Requirements of Law to which it is a party or by which it
         is or may be bound,  the failure of which could  reasonably be expected
         to have a material adverse effect on the performance of its obligations
         hereunder.

                                      -7-
<PAGE>

             (b) This Guaranty is a valid,  legal and binding obligation of the
         Guarantor,   subject  only  to  certain  exceptions  in  the  event  of
         bankruptcy and the application of general principles of equity.

             (c) The waivers,  representations,  warranties, covenants, and
         agreements  contained in this  paragraph  and this Guaranty are for the
         benefit of and may be  enforced  by the Credit  Bank and the Lessor and
         their respective successors and assigns.

             (d) The Guarantor has such knowledge of the business and financial
         affairs of the Lessee as the Guarantor  deems necessary to evaluate the
         risks of executing and delivering  this Guaranty to the Credit Bank and
         the Lessor,  and is capable of  evaluating  such risks by reason of the
         Guarantor's  knowledge and  experience.  All  information has been made
         available to the  Guarantor  by the Lessee  which is necessary  for the
         evaluation of such risks. The Guarantor has consulted with and received
         advice from legal counsel and  financial  advisers with respect to such
         risks  and the  Guarantor  has not  relied,  and  shall not rely in the
         future, upon the Lessor or the Credit Bank to conduct any investigation
         of the Lessee's financial  condition or business prospects or to notify
         the  Guarantor  now or in the future of any  adverse  information  with
         respect  thereto which could increase the  Guarantor's  risk under this
         Guaranty.

         11. The Guarantor agrees to repay, to  the extent  included within  the
Guaranteed  Obligations,  all monies,  including  but not limited to  reasonable
attorneys'  fees, paid by the Lessor in defense of any action  asserted  against
the  Lessor  by  the  Lessee,  as a  debtor-in-possession,  or by a  trustee  in
bankruptcy in a proceeding brought under 11 U.S.C. Section 547 of the Bankruptcy
Code for the  recovery  of monies  received  by the Lessor  from the Lessee as a
result of the Guarantor's obligations hereunder. The Guarantor further agrees to
repay any  monies  paid by the  Lessor in  settlement  of any such  action or in
satisfaction of any judgment rendered against the Lessor in such an action.

         12. The Guarantor hereby subordinates any  and all claims which it now
has, or in the future may acquire, as a creditor of any of the Lessee or Lessor,
to the prior payment and satisfaction in full of this Guaranty. If, prior to the
payment  and  satisfaction  of  this  Guaranty,  the  Guarantor  would,  without
reference  to the  provisions  of this  Section  12, be  entitled to receive any
payment on account of any claim of the  Guarantor  against  the Lessee or any of
its Subsidiaries,  or the Lessor, all such payments shall be made instead to the
Credit Bank until the  Guaranteed  Obligations  have been paid and  satisfied in
full, and the Guarantor hereby so directs. If the Guarantor receives any payment
on  account  of any  claim of the  Guarantor  against  the  Lessee or any of its
Subsidiaries,  or the Lessor,  the Guarantor shall immediately pay the same over
to  the  Credit  Bank  to be  applied  to the  payment  or  satisfaction  of the
Guaranteed Obligations,  if any. Notwithstanding the foregoing, unless an "Event
of Default" (as defined in the  Participation  Agreement) has occurred,  and has
not been  either  waived or  acknowledged  to have been  cured in writing by the
Credit Bank,  the Guarantor  may receive and retain  payments from the Lessee or
any of its  Subsidiaries  on account of any claim of the  Guarantor  against the
Lessee or any such Subsidiary.

                                      -8-
<PAGE>

         13. This Guaranty shall remain in full force and effect until payment
in full of all sums payable under and in respect of the Guaranteed  Obligations,
and all Operative  Documents with respect to the  Guaranteed  Obligations by the
Guarantor  hereunder  and the  performance  in full  of all  obligations  of the
Guarantor in accordance with the provisions of this Guaranty. This Guaranty is a
guaranty of payment and not of collection merely.

         14. In case any provision of this Guaranty or any  application  thereof
shall  be  invalid,  illegal  or  unenforceable,   the  validity,  legality  and
enforceability  of the remaining  provisions and any other  application  thereof
shall not in any way be affected or impaired thereby.

         15. TIME IS OF THE ESSENCE IN THIS GUARANTY AND THE TERMS HEREIN SHALL
BE SO  CONSTRUED.  This  Guaranty  shall be binding upon the  Guarantor  and its
successors and shall inure to the benefit of, and be enforceable  by, the Credit
Bank and its successors and assigns as to the obligations  respectively owed and
guaranteed hereunder.  This Guaranty may not be changed,  waived,  discharged or
terminated  orally,  but only by a statement in writing  signed by the Guarantor
and the  Credit  Bank,  in  compliance  with the  requirements  set forth in the
Participation  Agreement.  This  Guaranty  may be enforced as to any one or more
defaults either separately or cumulatively.  THIS GUARANTY SHALL IN ALL RESPECTS
BE GOVERNED BY, AND CONSTRUED AND ENFORCED IN ACCORDANCE  WITH,  THE LAWS OF THE
STATE OF GEORGIA.

         16. All notices,  demands,  requests,  consents  approvals and other
instruments  hereunder  shall  be  given in the  manner  and at the  appropriate
address set forth in the  Participation  Agreement  or at such other  address as
such party shall designate by notice to each of the other parties hereto.

         17. This  Guaranty is  made by the Guarantor solely to the Credit Bank
and the Lessor  and their  respective  successors  and  assigns,  and may not be
relied upon by any other person, firm, corporation or entity.

         18. The Guarantor waives any and all notice of the creation,  renewal,
extension or accrual of any of the amounts  which the  Guarantor is obligated to
pay  hereunder  and notice of or proof of  reliance by the Credit Bank upon this
Guaranty or  acceptance  of this  Guaranty.  The  indebtedness  evidenced by the
Guaranteed  Obligations  shall  conclusively  be deemed  to have  been  created,
contracted, incurred, renewed, extended, amended or waived in reliance upon this
Guaranty,  and all  dealings  between  the  Guarantor  and the Credit Bank shall
likewise be  conclusively  presumed to have been had or  consummated in reliance
upon this Guaranty.

         19. Notwithstanding  anything to the contrary  herein or in any other
Operative  Document,  any payment by the  Guarantor  to the Lessor or the Credit
Bank pursuant to any other Operative Document shall discharge  dollar-for-dollar
the related  obligations of the Guarantor to the Credit Bank hereunder,  and any
payment by the  Guarantor to the Credit Bank shall  discharge  dollar-for-dollar
the related  obligations of the Guarantor to the Lessor or the Credit Bank under
any other Operative Document.

         20. The Guarantor hereby irrevocably and  unconditionally (i) submits
for itself and its property in any legal action or  proceeding  relating to this
Guaranty or any other Operative

                                      -9-
<PAGE>

Document, or for recognition and enforcement of any judgment in respect thereof,
to the non-exclusive general jurisdiction of the courts of the State of Georgia,
the courts of the United States of America for the Northern  District of Georgia
and  appellate  courts from any thereof,  (ii)  consents that any such action or
proceedings may be brought to such courts,  and waives any objection that it may
now or hereafter have to the venue of any such action or proceeding in any court
or that such  action or  proceeding  was  brought in an  inconvenient  court and
agrees not to plead or claim the same,  (iii)  agrees that service of process in
any such  action or  proceeding  may be  effected  by mailing a copy  thereof by
registered  or  certified  mail (or any  substantially  similar  form of  mail),
postage  prepaid,  to such party at its  address set forth in SECTION 8.2 of the
Participation  Agreement  or at such other  address  of which the other  parties
hereto  shall have been  notified  pursuant to SECTION 8.2 of the  Participation
Agreement  and (iv) agrees that nothing  herein shall affect the right to effect
service of process in any other manner  permitted by law. The Guarantor,  to the
extent permitted by law, hereby irrevocably and unconditionally waives any right
to have a jury  participate  in  resolving  any  dispute,  whether  sounding  in
contract,  tort, or otherwise,  among or between the parties  hereto arising out
of,  in  connection  with,   related  to,  or  incidental  to  the  relationship
established  among the  parties  in  connection  with this  Guaranty,  any other
Operative  Document or any other  document  executed or delivered in  connection
herewith or the  transactions  related hereto.  This waiver shall not in any way
affect,  waive,  limit,  amend or modify the  Guarantor's  ability to pursue any
remedies contained in this Guaranty,  the other Operative Documents or any other
agreement or document related hereto.

         21. The Guarantor  acknowledges that (i) Lessor has assigned its rights
under this Guaranty to the Credit Bank  pursuant to the  Assignment of Lease and
Rents,  and the Lessor and the Credit Bank, by their  respective  acceptances of
this Guaranty, direct the Guarantor to make payments directly to the Credit Bank
of amounts  which at any time may become  due to the Lessor  hereunder  and (ii)
pursuant to the Assignment of Lease and Rents, the power to enforce the Lessor's
rights hereunder has been irrevocably granted to the Credit Bank pursuant to the
power of attorney set forth in SECTION 3 of the Assignment of Lease and Rents.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK]

                                      -10-
<PAGE>

         IN WITNESS  WHEREOF,  the Guarantor has caused this Limited Guaranty to
be duly executed as of the day and year first above written.

                                                   MINNESOTA POWER, INC.



                                                   By:  D. G. Gartzke
                                                      --------------------------
                                                   Its:
                                                       -------------------------



                                      -11-