(a) All notes or certificates of indebtedness issued for purposes authorized under Section 37-59-101, with the exception of the financing of school buses and transportation equipment, shall mature in approximately equal installments of principal and interest over a period not to exceed twenty (20) years from the date of issuance thereof. Provided, however, that if negotiable notes used to finance other such capital improvements are outstanding from not more than one (1) previous issue authorized under the provisions of this article, then the schedule of payments for a new or supplementary issue may be so adjusted that the schedule of maturities of all notes or series of notes hereunder shall, when combined, mature in approximately equal installments of principal and interest over a period of twenty (20) years from the date of the new or supplementary issue, or if a lower interest rate will be secured on notes previously issued and outstanding, a portion of the proceeds of any issue authorized hereunder may be used to refund the balance of the indebtedness previously issued under the authority of this article.

(b) All notes or certificates of indebtedness for purposes of financing of school buses and transportation equipment shall mature in approximately equal installments of principal and interest over a period not to exceed ten (10) years from the date of issuance thereof. Provided, however, that if negotiable notes used to finance such noncapital improvements are outstanding from not more than one (1) previous issue authorized under the provisions of this article, then the schedule of payments for a new or supplementary issue may be so adjusted that the schedule of maturities of all notes or series of notes hereunder shall, when combined, mature in approximately equal installments of principal and interest over a period of ten (10) years from the date of the new or supplementary issue, or if a lower interest rate will thereby be secured on notes previously issued and outstanding, a portion of the proceeds of any issue authorized hereunder may be used to refund the balance of the indebtedness previously issued under the authority of this article.