Document:

LOAN EXTENSION AGREEMENT
                           for Promissory Note held by
                             MERCANTILE BANK MIDWEST

1.       DATE AND PARTIES.  The date of this Extension Agreement  (Agreement) is
         November 10, 1999 and the parties are the following:

         BORROWER:
            TOP AIR MANUFACTURING, INC an Iowa corporation 317 Savannah Park Rd
            Cedar Falls, Iowa 50613 Tax I.D. # 42-1155462

         BANK:
            MERCANTILE BANK MIDWEST
            an IOWA banking corporation
            425 Cedar Street
            P.O. Box 88
            Waterloo, Iowa 50704
            Tax I.D. # 42-0167390

2.       BACKGROUND. Borrower executed a promissory note payable to the order of
         Bank dated  March 4, 1999,  (Note)  evidencing  a  revolving  draw loan
         (Loan) which Note is further described as follows:  Note number 254839,
         in the principal amount of  $6,000,000.00,  and payable on November 10,
         1999. As of the date of this  Agreement,  the principal  balance on the
         Note is  $1,909,000.00.  The total amount  currently due on the Note is
         $1,909,000.00. Borrower and Bank hereby agree to extend the Note on the
         terms contained in this Agreement.

3.       SECURITY.  To the extent not  prohibited  by law, the Note is and shall
         continue  to be  secured  by virtue of  cross-collateralization  by the
         following  described  security  agreements:  A Security Agreement dated
         November  2,  1998.  However,  the  Note  will not be  secured  by such
         security agreements if:

         A.    Bank  fails  to  make  any  disclosure  of the  existence  of the
               security agreements as required by law; or

         B.    to the extent such security  agreements are  "consumer"  loans in
               "household  goods"  (as those  terms are  defined  in  applicable
               federal   regulations   governing  unfair  and  deceptive  credit
               practices); or

         C.    to the  extent  such  security  agreements  are in  margin  stock
               subject to the requirements of 12 C.F.R. Section 207 or 221.

4.       TERMS. Borrower shall pay Bank as follows:

         A.    The Note is hereby  amended to provide that from the date of this
               Agreement, the principal of $6,000,000.00  (Principal) or so much
               thereof  as may,  from  time to time,  be  advanced  to  Borrower
               hereunder will accrue Interest from the date of disbursement,  on
               the  unpaid  principal  balance  at an  annual  rate  equal to .5
               percentage  point  below  Bank's  Prime  Rate,  as  adjusted  and
               announced  from  time to  time  until  the  Note  matures  or the
               obligation is  accelerated.  The Prime Rate,  minus .5 percentage
               points, may also be referred to hereafter as the "Contract Rate".

               "Prime  Rate" shall mean a rate per annum  equal to the  interest
               rate  announced  from time to time by  Mercantile  Bank  National
               Association  as its "prime rate" on Commercial  loans (which rate
               shall  fluctuate as and when said prime rate shall  change).  The
               Contract  Rate is the sum of Bank's Prime Rate  (8.25%)  minus .5
               percentage  point.  The  effective  Contract Rate today is 7.75%.
               Bank's  Prime Rate today is not  necessarily  the lowest  rate at
               which Bank lends its funds.  The Prime Rate is only an index rate
               from which Interest  rates  actually  charged to customers may be
               measured.  The use of the Prime Rate is for convenience  only and
               does  not  constitute  a  commitment  by Bank to lend  money at a
               preferred  rate of  interest.  The Prime Rate is a benchmark  for
               pricing certain types of loans.  Depending on the  circumstances,
               such as the amount and term of the loan, the  creditworthiness of
               the  borrower  or any  guarantor,  the  presence  and  nature  of
               collateral and other  relationships  between a borrower and Bank,
               loans may be priced at, above or below the Prime Rate.

               All  adjustments  to the  Contract  Rate will be made on each day
               that the Prime Rate  changes.  Any increase to the Prime Rate may
               be carried over to a subsequent adjustment date without resulting
               in a  waiver  or  forfeiture  of  such  adjustment,  provided  an
               adjustment  to the Contract Rate is made within one year from the
               date of such increase.  Any change in the Contract Rate will take
               the  form  of  different  payment  amounts.   After  maturity  or
               acceleration,  the unpaid balance shall bear interest at the rate
               specified  in the  Note  until  paid.  The  Loan and the Note are
               limited to the maximum lawful amount of interest  (Maximum Lawful
               Interest) permitted under federal and state laws. If the interest
               accrued and collected  exceeds the Maximum Lawful  Interest as of
               the time of  collection,  such excess  shall be applied to reduce
               the principal amount  outstanding,  unless otherwise  required by
               law. If or when no principal  amount is  outstanding,  any excess
               interest shall be refunded to Borrower according to the actuarial
               method.  Interest  shall be  computed  on the basis of the actual
               calendar year and the actual number of days elapsed.

         B.    Accrued  Interest is due and payable in I monthly payments on the
               10th day of each month,  beginning  December 10, 1999, or the day
               following  if the payment  day is a holiday or is a  non-business
               day for Bank.  Unless paid prior to maturity,  the last scheduled
               payment plus all unpaid principal,  accrued  interest,  costs and
               expenses  are due and payable on January 10,  2000,  which is the
               date of maturity.  If the Contract  Rate  changes,  any remaining
               payments may be a different amount.  All amounts shall be paid in
               legal  U.S.  currency.   Any  payment  made  with  a  check  will
               constitute payment only when collected.

         C.    This  Agreement  evidences an extension on a revolving  draw note
               and all advances  shall be made at the sole  discretion  of Bank.
               The amount of advances  under the Loan that are  outstanding  and
               unpaid shall never exceed  $6,000,000.00.  Interest  shall accrue
               only on the  amount of  outstanding  principal  that is drawn and
               unpaid under the Loan and this Agreement.

5.       WARRANTIES.  To  induce  Bank to enter  into this  Agreement,  Borrower
         warrants that:

         A.    Borrower has no existing  defenses or right of offset against the
               Note or any documents securing the Note.

         B.    Borrower reaffirms all of the terms of the Note and any documents
               securing the Note.

         C.    Since  the Note was  signed by  Borrower,  the  ownership  of the
               property  securing the Note has not been altered nor has any lien
               or  claim  been  filed or  threatened  to be  filed  against  the
               property (other than Bank's lien securing the Note).

6.       YEAR 2000  COMPLIANCE.  As of the date of this Agreement,  Borrower has
         assessed  the  risk  of Year  2000  noncompliance  and has  formulated,
         approved,  and  implemented  a  comprehensive  business plan (Year 2000
         Plan)  to meet  "Year  2000  requirements."  "Year  2000  requirements"
         include   analyzing,   programming,   and  testing  all  of  Borrower's
         information  technology  systems to  accurately  process  date and time
         data,  including,  but not  limited  to,  calculating,  comparing,  and
         sequencing functions.  "Year 2000 requirements" apply to all systems or
         processes that directly or indirectly affect Borrower's business,  such
         as accounting and processing  procedures,  as well as basic  electronic
         devices  that are  necessary to facility  management,  such as security
         systems, elevators, and telephones.  Borrower's Year 2000 Plan includes
         an allocation of resources  toward meeting Year 2000  requirements,  an
         inventory of all affected systems,  processes to assess and prepare for
         the interaction of Borrower's  systems with external systems,  periodic
         testing and evaluation of progress under Borrower's Year 2000 Plan, and
         contingency  arrangements for Year 2000 failure,  either by Borrower or
         Borrower's partners, affiliates, vendors, or customers.

         Borrower will take all measures  necessary to fulfill the  requirements
         of  Borrower's  Year 2000 Plan and meet all Year 2000  requirements  as
         specified  above.  Borrower  agrees to make  Borrower's  Year 2000 Plan
         available  to Bank,  if  requested,  and will  keep  Bank  informed  of
         progress  made  under   Borrower's   Year  2000  Plan.   Borrower  will
         immediately  notify Bank of any actual or anticipated delays in meeting
         dates  designated in Borrower's Year 2000 Plan or failure to accomplish
         any objectives of Borrower's Year 2000 Plan.  Borrower will allow Bank,
         or a third  party  Bank  designate,  reasonable  access  to  Borrower's
         information  technology systems for the purpose of determining progress
         made under Borrower's Year 2000 Plan.  Borrower agrees that Bank has no
         responsibility for managing,  advising,  or executing any of Borrower's
         efforts to comply with Year 2000  requirements  or Borrower's Year 2000
         Plan.

7.       CONTINUATION  OF  PROVISIONS.  Except  as  expressly  modified  in this
         Agreement,  all of the  provisions of the Note and any other  documents
         securing the Note remain in full force and effect.

8.       GENERAL PROVISIONS.

         A.    TIME IS OF THE  ESSENCE.  Time is of the  essence  in  Borrower's
               performance  of  all  duties  and  obligations  imposed  by  this
               Agreement.

         B.    NO  WAIVER  BY  BANK.   Bank's  course  of  dealing,   or  Bank's
               forbearance  from,  or delay in,  the  exercise  of any of Bank's
               rights,  remedies,  privileges or right to insist upon Borrower's
               strict performance of any provisions contained in this Agreement,
               or other loan  documents,  shall not be  construed as a waiver by
               Bank, unless any such waiver is in writing and is signed by Bank.

         C.    AMENDMENT.  The provisions contained in this Agreement may not be
               amended,  except through a written  amendment  which is signed by
               Borrower and Bank.

         D.    INTEGRATION  CLAUSE.  This written  Agreement  and all  documents
               executed    concurrently    herewith,    represent   the   entire
               understanding  between the parties as to the  Obligations and may
               not be  contradicted  by evidence of prior,  contemporaneous,  or
               subsequent oral agreements of the parties.

         E.    FURTHER  ASSURANCES.  Borrower  agrees,  upon request of Bank and
               within the time Bank specifies,  to provide any information,  and
               to execute, acknowledge,  deliver and record or file such further
               instruments or documents as may be required by Bank to secure the
               Note or confirm any lien.

         F.    GOVERNING  LAW. This  Agreement  shall be governed by the laws of
               the State of IOWA,  provided  that  such  laws are not  otherwise
               preempted by federal laws and regulations.

         G.    FORUM AND VENUE.  In the event of  litigation  pertaining to this
               Agreement,  the exclusive forum,  venue and place of jurisdiction
               shall be in the State of IOWA,  unless  otherwise  designated  in
               writing by Bank or otherwise required by law.

         H.    SUCCESSORS. This Agreement shall inure to the benefit of and bind
               the heirs,  personal  representatives,  successors and assigns of
               the  parties;  provided  however,  that  Borrower may not assign,
               transfer or delegate any of the rights or obligations  under this
               Agreement.

         I.    NUMBER AND GENDER.  Whenever used, the singular shall include the
               plural, the plural the singular,  and the use of any gender shall
               be applicable to all genders.

         J.    DEFINITIONS.  The terms used in this  Agreement,  if not  defined
               herein,  shall  have  their  meanings  as  defined  in the  other
               documents  executed  contemporaneously,  or in conjunction,  with
               this Agreement.

         K.    PARAGRAPH  HEADINGS.   The  headings  at  the  beginning  of  any
               paragraph,  or  any  subparagraph,  in  this  Agreement  are  for
               convenience  only and shall not be dispositive in interpreting or
               construing this Agreement.

         L.    IF HELD  UNENFORCEABLE.  If any provision of this Agreement shall
               be held  unenforceable or void, then such provision to the extent
               not  otherwise  limited  by  law  shall  be  severable  from  the
               remaining   provisions   and   shall   in  no  way   affect   the
               enforceability  of the remaining  provisions  nor the validity of
               this Agreement.

         M.    CHANGE IN APPLICATION. Borrower will notify Bank in writing prior
               to any change in Borrower's name,  address,  or other application
               information.

         N.    NOTICE. AlI notices under this Agreement must be in writing.  Any
               notice given by Bank to Borrower hereunder will be effective upon
               personal delivery or 24 hours after mailing by first class United
               States  mail,  postage  prepaid,  addressed  to  Borrower  at the
               address  indicated  below  Borrower's  name on  page  one of this
               Agreement. Any notice given by Borrower to Bank hereunder will be
               effective  upon  receipt by Bank at the address  indicated  below
               Bank's name on page one of this Agreement.  Such addresses may be
               changed by written notice to the other party.

9.       ADDITIONAL TERMS. This loan is subject to the terms and conditions of a
         Loan Agreement dated November 2, 1998.

10.      RECEIPT  OF  COPY,  Borrower  acknowledges  receiving  a copy  of  this
         Agreement.

<PAGE>

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                        IMPORTANT: READ BEFORE SIGNING.

THE TERMS OF THIS AGREEMENT SHOULD BE READ CAREFULLY BECAUSE ONLY THOSE TERMS IN
WRITING ARE  ENFORCEABLE.  NO OTHER TERMS OR ORAL PROMISES NOT CONTAINED IN THIS
WRITTEN  CONTRACT  MAY BE  LEGALLY  ENFORCED.  YOU MAY  CHANGE THE TERMS OF THIS
AGREEMENT ONLY BY ANOTHER WRITTEN AGREEMENT.

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

BORROWER:

     TOP AIR MANUFACTURING, INC an
       Iowa corporation
                                                              [Corporate Seal*]
       By: /s/ Steven R. Lind
           --------------------------------------
            STEVE R. LIND, PRESIDENT

(*Corporate seal may be affixed,  but failure to affix shall not affect validity
or reliance.)

       APPROVED: November 10, 1999

       BANK:
              MERCANTILE BANK MIDWEST
              an IOWA banking corporation
                                                              [Corporate Seal*]
               By:  /s/ Steve D. Brewer
                   ------------------------------
                   STEVE D. BREWER,
                   EXEC. VICE PRESIDENT

(*Corporate seal may be affixed,  but failure to affix shall not affect validity
or reliance.)

THIS IS THE LAST PAGE OF A 2 PAGE DOCUMENT. EXHIBITS AND/OR ADDENDA MAY FOLLOW.AGREEMENT

         This  Agreement is made this 28th day of January,  2000, by and between
MERCANTILE  BANK  MIDWEST  ("Bank"),  TOP  AIR  MANUFACTURING,   INC.,  an  Iowa
corporation,   ("Top  Air"),  PARKER  INDUSTRIES,  INC.,  an  Iowa  corporation,
("Parker"),  and PARKER  ACQUISITION  SUB, INC., an Iowa  corporation,  ("Parker
Sub").

                                    RECITALS

         WHEREAS,  Top Air and  Bank  entered  into a  November  2,  1998,  Loan
Agreement,  which  was  modified  by a March 4,  1999,  Modification  Agreement,
(collectively, the "Loan Agreement"); and

         WHEREAS,  Top  Air  borrowed  money  pursuant  to said  Loan  Agreement
evidenced by  promissory  note No.  254839 dated March 4, 1999, as extended by a
written Loan  Extension  Agreement  dated November 10, 1999  (collectively,  the
"Note"); and

         WHEREAS,  the Note is secured by certain  assets of Top Air and certain
assets of Top Air's subsidiaries, Parker and Parker Sub; and

         WHEREAS,  Top Air is in  default  under  the terms of the Note and Loan
Agreement,  but  Bank has  agreed,  notwithstanding  such  default,  to  forbear
exercising its rights and remedies under the Note and Loan  Agreement,  provided
Top Air,  Parker and Parker Sub  perform  all the terms and  conditions  of this
Agreement as hereinafter set forth;

         NOW, THEREFORE, IT IS AGREED AS FOLLOWS:

         1. Simultaneously  with the execution of this Agreement,  Top Air shall
execute and deliver to Bank an Overadvance Line of Credit  Promissory Note and a
Line of Credit Promissory Note, (collectively, the "New Notes"), copies of which
are attached  hereto as Exhibits "A" and "B"  respectively.  The New Notes shall
replace Top Air's  indebtedness under the Note, but all the terms and conditions
of the Note and Loan Agreement,  except as modified in the New Notes and in this
Agreement,  shall continue in full force and effect,  and Bank shall continue to
be entitled to all of the rights, remedies, benefits and security provided under
the Loan  Agreement  and Note.  The aggregate  balance of all principal  amounts
advanced  under the New Notes  shall  never  exceed the sum of Six  Million  and
00/100 Dollars ($6,000,000.00).

         2. The New Notes shall be payable  according to the terms thereof,  but
shall be due and payable in full, in any event, on April 18, 2000.

         3. Effective with the Borrowing Base  Certificate due February 1, 2000,
for the period ending December 31, 1999,  there shall be excluded from "eligible
accounts  receivable"  the total  customer  balance  (100%) for any account with
respect to which twenty-five percent (25%) or more of the balance is over ninety
(90) days past due. Except to the extent otherwise provided herein,  none of the
accounts  receivable  purchased  by Top Air and/or  Parker  Sub from DWZM,  Inc.
and/or Owosso  Corporation  pursuant to an Asset Purchase  Agreement dated as of
March 3, 1999 (the "Owosso Receivables") shall be included in the Borrowing Base
Certificate.  The "total  customer  balance" for any account  shall  include all
amounts owed by the customer  with respect to purchases  from Top Air,  plus all
amounts owed by the customer  that make up part of the Owosso  Receivables.  Any
payments  received  by Top Air with  respect  to the Owosso  Receivables  may be
applied either to Top Air's  obligations to Bank, or to Top Air's obligations to
DWZM, Inc. and/or Owosso Corporation under the Asset Purchase Agreement dated as
of March 3, 1999 (the "Owosso Debt"). In no event shall any payments received by
Top Air from receivables other than the Owosso  Receivables be applied to any of
the Owosso Debt.  In addition,  within ten (10) days after the execution of this
Agreement,  Top Air shall provide to Bank a complete and current  listing of all
of its  accounts  receivable,  including,  but  not  limited  to,  all  accounts
receivable  purchased by Top Air and/or Parker Sub from DWZM, Inc. and/or Owosso
Corporation  pursuant to an Asset Purchase  Agreement dated as of March 3, 1999.
Top Air's  "eligible  accounts  receivable"  for purposes of its Borrowing  Base
Certificate  shall not  include any  accounts  that are not  identified  on such
listing,  or on such  future  listings  as Top Air shall  provide  to Bank.  All
monthly financial  information that Top Air is required to provide to Bank under
the terms of the Note and Loan  Agreement  shall be provided  within thirty (30)
days after the end of each calendar month, effective December 3 1, 1999.

         4. Simultaneously  with the execution of this Agreement,  Top Air shall
provide Bank with a  file-stamped  copy of a UCC-3  Termination  Statement  with
respect to UCC-1 Financing  Statement  #K666812 filed with the Iowa Secretary of
State of July 31, 1995, and a file-stamped copy of a UCC-3 Termination Statement
with respect to UCC-1 Financing Statement #K989290 filed with the Iowa Secretary
of  State  on  February  5,  1999.  For as long  as Top Air has any  outstanding
obligation  to Bank,  Top Air shall not grant or permit the  placing of any lien
against any of the property  securing Top Air's  obligations  to Bank, and shall
not pay any amount to any  creditor  holding a lien  against any such  property,
without Bank's prior written consent.

         5. Top Air, as further  security for its  obligations  to Bank,  hereby
grants Bank a security  interest in, and assigns to Bank, all of Top Air's right
to receive 20.5% of the proceeds of the sale of the real property at 317 Savanah
Park Road, Cedar Falls, Iowa 50613 (the "Real  Property").  The Real Property is
currently owned by the City of Cedar Falls,  Iowa, subject to Top Air's right to
receive  20.5% of the  proceeds  of the sale of the  Real  Property  if the Real
Property is sold.

         6. From and after the execution of this Agreement, Top Air shall comply
with all of the  Affirmative  Covenants and Negative  Covenants  provided in the
Note and Loan Agreement as though fully set forth herein.  Top Air  acknowledges
and agrees that it is currently in default of such Covenants  under the Note and
Loan Agreement.  Notwithstanding such default,  Bank agrees that it will take no
action  against Top Air as a result of such  default,  provided Top Air complies
with all the terms and conditions of this Agreement, and Top Air does not cause,
permit or allow any further  defaults  with respect to such  Covenants  from and
after the execution of this Agreement.

         7. Top Air represents, guaranties and warrants to Bank that:

               A. Top Air is an Iowa  corporation  authorized  to do business in
         the State of Iowa and in each state where it may be doing  business and
         has full power and authority to execute and deliver this  Agreement and
         all documents incident thereto;

               B. Top Air is duly  incorporated and validly existing and in good
         standing in the State of Iowa, and in each  jurisdiction  where Top Air
         conducts business;

               C. This  Agreement,  and all  documents  incident  thereto,  will
         constitute  legal,  valid,  and binding  agreements and are enforceable
         against Top Air and all other parties thereto;

               D. Top Air has  good and  marketable  title  to its  assets,  and
         enjoys peaceful and undisturbed possession under all leases under which
         Top Air now operates;

               E. Top Air is  complying  with all  applicable  federal  or state
         labor  laws,  including  but not  limited  to the  Federal  Fair  Labor
         Standards Act;

               F. Top Air has  complied  with all  federal,  state and local tax
         laws, licensing laws and permit laws;

               G. Top Air is not in  violation  of other  federal  laws or state
         laws,  including but not limit to, ERISA  (Employee  Retirement  Income
         Security Act) or RICO (Racketeer Influenced and Corrupt Organizations);

               H. Top Air is in  compliance  with all laws,  orders,  judgments,
         decrees and  regulations  ("Laws") of all federal,  foreign,  state and
         local, governmental authorities relating to the business operations and
         the assets of Top Air,  the  violation  of which  would have an adverse
         effect  on the  value  of or  Bank's  interest  in any of the  property
         securing  Top Air's  obligations  to Bank,  or would have a  materially
         adverse effect on Top Air's financial condition, business or conduct of
         its business;

               I.  Top  Air is not a party  to,  nor is Top Air  bound  by,  any
         agreement  that  materially  or adversely  affects Top Air's  business,
         properties, assets or operations;

               J. There are no outstanding  claims or rights that would conflict
         with the execution,  delivery or performance by Top Air of the terms of
         this Agreement or the documents incident thereto, or that would cause a
         lien to be placed on any of the property securing Top Air's obligations
         to Bank,  except those,  if any,  disclosed to and agreed to by Bank in
         writing;

               K. All  financial  statements,  books,  records,  documents,  and
         instruments  submitted by Top Air to Bank in  connection  with the Loan
         Agreement,  Note,  and this  Agreement are accurate and  complete,  and
         there has been no material adverse change in the financial condition of
         Top Air as shown  by such  statements,  books,  records,  documents  or
         instruments;

               L. Top Air is solvent,  able to pay its debts as they mature, and
         has  sufficient  capital to carry on its business and all businesses in
         which Top Air is or will be  engaged.  Top  Air's  total  assets,  at a
         present,  fair market  value,  are greater than the amount of Top Air's
         total  obligations.  Top Air  will  not be  rendered  insolvent  by the
         execution of this Agreement or the documents incident thereto;

               M.  There are no  proceedings  pending or  threatened  before any
         court or  administrative  agency  which will or could have a materially
         adverse effect upon the financial condition or operations of Top Air;

               N. All  representations,  warranties,  statements  guaranties and
         covenants  contained in the Loan  agreement,  Note or this Agreement or
         any  documents  incident  thereto,  shall survive the execution of such
         documents.

         8. To induce Bank to enter this Agreement, Top Air:

               A. Warrants  that it has no existing  defenses or right of offset
         against the Note,  Loan  Agreement  or any other  document  executed in
         connection therewith;

               B. Reaffirms all of its obligations  under the Loan Agreement and
         Note and any other documents executed in connection therewith;

               C. Warrants that since the Note and Loan Agreement were signed by
         Top Air, the  ownership of the property  securing the Note has not been
         altered nor has any lien or claim been filed or  threatened to be filed
         against the property securing Top Air's obligations to Bank;

               D. For itself, its successors and assigns, hereby irrevocably and
         unconditionally  releases and forever  discharges  Bank, its employees,
         officers,  attorneys,  representatives  and  assigns  from  any and all
         claims and defenses  with respect to the Note,  Loan  Agreement and any
         other  documents  executed in  connection  therewith  that have been or
         could be asserted against Bank as of the date of this Agreement.

         9. Each party is executing this Agreement solely in reliance upon their
own knowledge,  belief and judgment and not upon the representations made by any
other party or others on their behalf.

         10. This  Agreement  shall be binding  upon and inure to the benefit of
and shall be  enforceable  by the  parties  hereto,  their  respective  personal
representatives, heirs, administrators, successors and assigns.

         11. Except as modified by this Agreement and the New Notes,  all of the
terms and conditions of the Note and Loan Agreement remain unchanged and in full
force and effect.

         12.  No delay or  failure  by Bank to  exercise  any right  under  this
Agreement,  and no partial or single exercise of that right,  shall constitute a
waiver of that or any other right, unless otherwise express provided by Bank.

         13. Top Air acknowledges receiving a copy of this Agreement.

--------------------------------------------------------------------------------
                         IMPORTANT: READ BEFORE SIGNING.
--------------------------------------------------------------------------------

THE TERMS OF THIS AGREEMENT SHOULD BE READ CAREFULLY BECAUSE ONLY THOSE TERMS IN
WRITING ARE  ENFORCEABLE.  NO OTHER TERMS OR ORAL PROMISES NOT CONTAINED IN THIS
WRITTEN  CONTRACT  MAY BE  LEGALLY  ENFORCED.  YOU MAY  CHANGE THE TERMS OF THIS
AGREEMENT ONLY BY ANOTHER WRITTEN AGREEMENT.

TOP AIR MANUFACTURING, INC.                MERCANTILE BANK MIDWEST

By: /s/ Steven R. Lind, Pres.              By:
   -------------------------------             ---------------------------------

PARKER INDUSTRIES, INC.

By:  /s/ Steven R. Lind, Pres.
    ------------------------------

PARKER ACQUISITION SUB, INC.

By:  /s/ Steven R. Lind, Pres.
    ------------------------------

<PAGE>

                   OVERADVANCE LINE OF CREDIT PROMISSORY NOTE

Maximum Line of Credit: $1,000,000.00                        January 28, 2000
                                                             Cedar Rapids, Iowa

         FOR VALUE RECEIVED,  Top Air  Manufacturing,  Inc., an Iowa Corporation
(the  "Borrower"),  hereby promises to pay Mercantile Bank Midwest (the "Bank"),
at 222 Second  Avenue S.E.,  Cedar  Rapids,  Iowa 52401,  the  aggregate  unpaid
principal  balance of all  extensions of credit made by the Bank to the Borrower
up to the Maximum Line of Credit  available to Borrower under this Note pursuant
to the Loan  Agreement by and between  Borrower and Bank dated November 2, 1998,
as modified by a written Modification Agreement on March 4, 1999, and as further
modified by a written Agreement dated January 28, 2000, between the Bank and the
Borrower (collectively,  the "Agreement"),  together with interest from the date
hereof  on the  unpaid  principal  balance  from time to time  outstanding  (the
"Balance"),  in lawful  money of the United  States of  America  in  immediately
available  funds as  required  by the terms of the  Agreement.  This Note  shall
mature on April 18, 2000,  and Borrower  shall repay in full not later than such
maturity  date the  Balance,  together  with all  interest  and charges  accrued
thereon and unpaid as of such date.

         The Balance shall bear interest at a rate per annum equal to the Bank's
floating Prime Rate as established  from time to time,  plus 3%, payable monthly
in arrears on the first day of each month  commencing  February 1, 2000,  and at
maturity.  Each change in the rate of interest  hereon shall be effective on the
date of the  corresponding  change in the Prime Rate. In no event shall the rate
stated  herein,  either  prior to or after  default,  exceed  the  maximum  rate
permitted by law for transactions of this type.

         The Balance shall be paid by Borrower in installments of $208,000 on or
before January 31, 2000, $208,000.00 on or before February 29, 2000, $208,000.00
on or before March 31, 2000, and the entire remaining Balance on or before April
18, 2000.

         This Note, along with a Line of Credit Promissory Note executed of even
date herewith, replaces a portion of Borrower's indebtedness under the Agreement
evidenced by  promissory  note No.  254839 dated March 4, 1999, as extended by a
written Loan Extension  Agreement  dated November 10, 1999,  (collectively,  the
"Note").  Except as otherwise  provided herein,  all the terms and conditions of
the Note and Agreement continue in full force and effect, and the Bank continues
to be entitled to all of the rights,  remedies,  benefits and security  provided
under the  Agreement  and Note.  The  Borrower  may, at its option,  at any time
prepay all or any portion of the Balance. Borrower hereby waives any requirement
of presentment, demand, notice, and diligence in bringing suit.

         This Note shall be governed by and  construed  in  accordance  with the
laws of the State of Iowa.

                                       TOP AIR MANUFACTURING, INC.

                                       By: /s/ Steven R. Lind
                                           -------------------------------------
                                           Steven R. Lind, President

<PAGE>

                         LINE OF CREDIT PROMISSORY NOTE

Maximum Line of Credit: $5,000,000.00                        January 28, 2000
                                                             Cedar Rapids, Iowa

         FOR VALUE RECEIVED,  Top Air  Manufacturing,  Inc., an Iowa Corporation
(the  "Borrower"),  hereby promises to pay Mercantile Bank Midwest (the "Bank"),
at 222 Second  Avenue S.E.,  Cedar  Rapids,  Iowa 52401,  the  aggregate  unpaid
principal  balance of all  extensions of credit made by the Bank to the Borrower
up to the Maximum Line of Credit  available to Borrower under this Note pursuant
to the Loan  Agreement by and between  Borrower and Bank dated November 2, 1998,
as modified by a written Modification Agreement on March 4, 1999, and as further
modified by a written Agreement dated January 28, 2000, between the Bank and the
Borrower (collectively,  the "Agreement"),  together with interest from the date
hereof  on the  unpaid  principal  balance  from time to time  outstanding  (the
"Balance"),  in lawful  money of the United  States of  America  in  immediately
available  funds as  required  by the terms of the  Agreement.  This Note  shall
mature on April 18, 2000,  and Borrower  shall repay in full not later than such
maturity  date the  Balance,  together  with all  interest  and charges  accrued
thereon and unpaid as of such date.

         The Balance shall bear interest at a rate per annum equal to the Bank's
floating Prime Rate as established  from time to time,  plus 1/4 %, and shall be
payable in accordance with the terms of the Agreement,  provided that the entire
Balance and all accrued  interest shall mature and be due and payable in full on
April 18, 2000. Each change in the rate of interest hereon shall be effective on
the date of the  corresponding  change in the Prime Rate.  in no event shall the
rate stated herein,  either prior to or after  default,  exceed the maximum rate
permitted by law for transactions of this type.

         This Note,  along with an Overadvance  Line of Credit  Promissory  Note
executed of even date  herewith,  replaces a portion of Borrower's  indebtedness
under the Agreement evidenced by promissory note No. 254839 dated March 4, 1999,
as extended by a written  Loan  Extension  Agreement  dated  November  10, 1999,
(collectively,  the "Note").  Except as otherwise provided herein, all the terms
and conditions of the Note and Agreement  continue in full force and effect, and
the Bank continues to be entitled to all of the rights,  remedies,  benefits and
security provided under the Agreement and Note. The Borrower may, at its option,
at any time,  prepay  all or any  portion  of the  Balance,  without  premium or
penalty,  all subject to and in accordance with the provisions hereof and of the
Agreement.  Borrower  hereby  waives any  requirement  of  presentment,  demand,
notice, and diligence in bringing suit.

         This Note shall be governed by and  construed  in  accordance  with the
laws of the State of Iowa.

                                       TOP AIR MANUFACTURING, INC.

                                       By: /s/ Steven R. Lind
                                           -------------------------------------
                                           Steven R. Lind, President

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