(a) Rents or charges for the use of the exhibition grounds and buildings precedent to the issuance of bonds shall not be reduced until all of the bonds shall have been fully paid and may, whenever necessary, be increased in amounts sufficient to provide for the payment of the bonds, both principal and interest, and to provide proper funds for the depreciation account and operation and maintenance charges.

(b)

(1) If any surplus shall be accumulated in the operating and maintenance fund which shall be in excess of the cost of maintaining and operating the project during the remainder of the fiscal year then-current, and the cost of maintaining and operating the project during the fiscal year then-ensuing, then any excess may be transferred by the legislative body to either the depreciation account or to the bond and interest redemption account, as the legislative body may designate.

(2) If any surplus shall be accumulated in the depreciation account over and above that which the legislative body shall find may be necessary for the probable replacement which may be needed during the then-present fiscal year and the ensuing fiscal year, the excess may be transferred to the bond and interest redemption account.

(3) If surplus shall exist in the bonds and interest redemption account, it shall be applied insofar as possible in the purchase or retirement of outstanding revenue bonds payable from the account. For that purpose, the legislative body is authorized to purchase bonds not due in the open market at not more than the fair market value thereof.