(a) Except where section 4502.5(c) of this Part justifies extension of the contract payment date, RIOC shall be liable for payment of interest on the contract if payment is made later than the date specified in section 4502.5(a) of this Part, in which case interest shall be calculated from the payment due date specified in section 4502.5(a) until the final payment date.

(b) Interest shall be computed at the rate equal to the rate set by the New York State Tax Commission for corporate taxes pursuant to section 1096(e)(1) of the Tax Law.