Section 9-512 - Issuance of bonds; service ratesA. The municipal corporation, for any and all purposes provided in section 9-511, may issue and sell bonds bearing interest not to exceed nine per cent per annum.B. When the enterprise or public improvement has been purchased or constructed by means derived from the sale of bonds, the municipality shall fix the rates charged for service to the public as nearly as practicable so as to pay the interest and not less than three per cent per annum on the principal of the bonds, in excess of the expense of maintenance and operation.