Document:

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                                                                   EXHIBIT 10.16

                        REVOLVING CREDIT PROMISSORY NOTE

$5,000,000.00                                                 March 29, 2001

         FOR VALUE RECEIVED, the undersigned, OPTIO SOFTWARE, INC. (the
"Borrower"), hereby promises to pay to the order of BRANCH BANKING AND TRUST
COMPANY ("Bank"), at its branch office in Atlanta, Georgia, in lawful money of
the United States and in immediately available funds, the principal amount of
FIVE MILLION DOLLARS ($5,000,000.00) or, if less, the aggregate unpaid principal
balance outstanding upon the termination of the Loan Agreement, as defined
hereinbelow, and to pay interest (computed on the basis of a year consisting of
360 days for the actual number of days for which a principal balance is
outstanding hereunder) from the date hereof on the unpaid principal balance from
time to time outstanding at a rate per annum equal to the Prime Rate, as
hereinafter defined, plus one-half percent (00.50%) per annum, payable on the
first day of each month commencing April 1, 2001, through maturity. On the date
hereof, the Prime Rate is 8.0% and, therefore, the rate of interest in effect
hereunder with respect to this Revolving Credit Promissory Note on the date
hereof, expressed in simple interest terms, is 8.5%.

         Any principal amount which is not paid when due, whether at maturity,
by acceleration or otherwise, shall bear interest from the date when due until
such principal amount is paid in full at a rate per annum equal to the Default
Rate, as defined below. If any payment is to be made on a day other than a day
on which Bank is open for business ("Business Day"), the maturity shall be
extended to the next succeeding Business Day, and interest shall be payable at
the rate in effect during such extension.

         The term "Prime Rate" used in this Note means the prime rate as defined
in the Loan Agreement, as defined hereinbelow. The term "Default Rate" as used
in this Note means the fluctuating rate of interest per annum equal to the Prime
Rate plus 5.00%.

         This Note evidences the indebtedness and obligations of Borrower under
that certain Loan and Security Agreement between the Borrower and Bank dated as
of March 29, 2001 ("Loan Agreement"), and is secured by certain collateral
described therein, including without limitation, all of Borrower's now owned and
hereafter acquired accounts, contract rights, inventory, equipment, documents,
instruments, investment property, chattel paper and general intangibles.
Reference is made to the Loan Agreement for a complete description of the
collateral and the rights of the parties therein, including the maturity date
hereof, which Loan Agreement is incorporated by reference herein.

          Upon the occurrence of an Event of Default, as defined in the Loan
Agreement, Bank shall have the option of declaring the entire outstanding
principal balance of this Note and all accrued interest immediately due and
payable. If, after the occurrence of an Event of Default or maturity, this Note
is referred to an attorney for collection or enforcement, or for representation
in a bankruptcy or other reorganization or insolvency type proceeding or action,
Borrower shall

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pay all costs and expenses of collection or enforcement actually incurred,
including, without limitation, reasonable attorneys' fees.

         No delay or omission on the part of the holder of this Note in
exercising any right hereunder shall operate as a waiver of such right or of any
other right of such holder, nor any delay, omission, or waiver on any one
occasion be deemed a bar to or a waiver of the same or of any other right on any
future occasion. Borrower and each endorser of this Note, regardless of the
time, order or place of signing, waives presentment, demand, protest and notices
of every kind, and consents to any one or more extensions or postponements of
the time of payment or any other indulgences, to any substitutions, exchanges or
releases of collateral if at any time there shall be available to the holder
collateral for this Note, and to the additions or releases of any other parties
or person primarily or secondarily liable herefor.

         From time to time the maturity date of this Note may be extended, or
this Note may be renewed in whole or in part, or a new note of different form
may be substituted for this Note, or the rate of interest may be modified, with
Borrower's consent, or changes may be made in consideration of loan extensions,
and the holder hereof, from time to time may waive or surrender, either in whole
or in part any rights, guaranties, secured interest, or liens, given for the
benefit of the holder in connection with the payment and the securing the
payment of this Note; but no such occurrence shall in any manner affect, limit,
modify, or otherwise impair any rights or security of the holder not
specifically waived, released, or surrendered in writing, nor shall the
Borrower, any endorser, or any person who is or might be liable hereon, either
primarily or contingently, be released from such liability by reason of the
occurrence of any such event.

         This Note is made in and shall be governed by the laws of Georgia, and
shall be binding on the successors and assigns of the Borrower.

         IN WITNESS WHEREOF, the Borrower's duly authorized officer has executed
this Note on behalf of the Borrower and its Secretary has attested his signature
and affixed the corporate seal on the date first shown above.

<TABLE>
<S>                                      <C>
                                         OPTIO SOFTWARE, INC.
ATTEST:

By: /s/ Barron Hughes                    By: /s/ Barron Hughes
   ------------------------                 -----------------------
        Secretary                        Title: CFO
</TABLE>

[CORPORATE SEAL]

                                      -2-<PAGE>

                                                                    Exhibit 4.2

                         [FORM OF FACE OF CERTIFICATE]

              Organized Under the Laws of the State of South Dakota

                                                         CLASS B CAPITAL UNITS
B-

                            GREAT PLAINS ETHANOL, LLC

 THIS CERTIFIES THAT__________________________________________ IS THE OWNER AND
 REGISTERED HOLDER OF_____________________________________________ CLASS B
 CAPITAL UNITS

                          in Great Plains Ethanol, LLC

TRANSFERABLE ONLY ON THE BOOKS OF THE LIMITED LIABILITY COMPANY BY THE HOLDER
HEREOF IN PERSON OR BY DULY AUTHORIZED ATTORNEY UPON SURRENDER OF THIS
CERTIFICATE PROPERLY ENDORSED.

              IN WITNESS WHEREOF, THE SAID LIMITED LIABILITY COMPANY HAS CAUSED
              THIS CERTIFICATE TO BE SIGNED BY ITS DULY AUTHORIZED OFFICERS THIS
                    DAY OF           , 200__.

  _________________                                          _________________
      SECRETARY                                                  PRESIDENT

<PAGE>

                        [FORM OF REVERSE OF CERTIFICATE]

             The Capital Units represented by this Certificate have
           not been registered under the Securities Act of 1933, as
             amended (the "Act"), or applicable Blue Sky laws. The
          securities may not be sold, offered for sale or transferred
           in the absence of an effective registration under the Act
          and such applicable Blue Sky laws, or an opinion of counsel
              satisfactory to Great Plains Ethanol, LLC that such
                         registration is not required.

             The sale and transfer of the Capital Units represented
          by this Certificate are also restricted by, and subject to,
               the provisions of the Operating Agreement of Great
             Plains Ethanol, LLC. The Operating Agreement provides,
             among other things, that no sale, assignment, transfer,
              gift, exchange or other disposition of these Capital
              Units is valid except as specifically provided for in
                the Operating Agreement. Copies of the Operating
             Agreement and instructions for transfer, sale or other
              disposition of these Capital Units are available for
                  inspection at the Company's principal office.

FOR VALUE RECEIVED __________ HEREBY SELL, ASSIGN AND TRANSFER UNTO
___________________________________________________________________
____________________________________________________ CAPITAL UNITS REPRESENTED
BY THE WITHIN CERTIFICATE, AND DO HEREBY IRREVOCABLY CONSTITUTE AND APPOINT
____________________________________________________ ATTORNEY TO TRANSFER THE
SAID CAPITAL UNITS ON THE BOOKS OF THE WITHIN NAMED LIMITED LIABILITY COMPANY
WITH FULL POWER OF SUBSTITUTION IN THE PREMISES.
DATED         ____________________, 20_____ __________________

IN PRESENCE OF ___________________________________________________

NOTICE: THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS
WRITTEN UPON THE FACE OF THIS CERTIFICATE IN EVERY PARTICULAR, WITHOUT
ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.<PAGE>

                                                                  Exhibit 10(a)

INDEPENDENT AUDITORS' CONSENT

We consent to the use in this Post-Effective Amendment No. 24 to Registration
Statement No. 2-78738 of Sun Life of Canada (U.S.) Variable Account C on Form
N-4 of our report dated February 9, 2001 accompanying the financial
statements of Sun Life of Canada (U.S.) Variable Account C and to the use of
our report dated February 7, 2001 accompanying the financial statements of
Sun Life Assurance Company of Canada (U.S.), appearing in the Statement
of Additional Information, which is part of such Registration Statement,
and to the incorporation by reference of our report dated February 7, 2001,
appearing in the Annual Report on Form 10-K of Sun Life Assurance
Company of Canada (U.S.) for the year ended December 31, 2000.

We also consent to the reference to us under the heading "Condensed
Financial Information -- Accumulation Unit Values" appearing in the
Prospectus which is part of such Registration Statement, and under the
heading "Accountants" in such Statement of Additional Information.

DELOITTE & TOUCHE LLP
Boston, Massachusetts

April 30, 2001

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