408.105.  Precomputed loans, extensions, fee, limitations. — 1.  Extensions on precomputed loans made pursuant to section 408.100 shall be calculated on an actuarial basis or as follows and shall not be considered an additional charge or fee within the meaning of section 408.140:

  2.  The following limitations regarding extensions on precomputed loans shall apply:

  (1)  No extension may be taken on the first installment;

  (2)  No extension fee shall be collected more than one month prior to the due date of the earliest installment being deferred;

  (3)  No extension shall be collected for any partial payment; however, two dollars or less shall not be considered a partial payment;

  (4)  A minimum extension fee of one dollar will be allowed;

  (5)  In the event of^* prepayment in full of the note or contract, the extensions shall be counted as months and computed as provided in section 408.170, based on this total, applied to all of the interest contracted for, plus the extension fees collected.