When any loan is prepaid, the amount of interest earned must be computed by applying the agreed rate to the unpaid balance for each period. Any greater amount of interest which may have been precomputed and included in the balance due must be allowed as a credit on any amount due or refunded. This section does not preclude the imposition of any:
1. Penalty for prepayment; or
2. Single charge for making the loan,
to which the parties agree when the loan is made.
(Added to NRS by 1983, 976)