(a) The governing body or other proper officers having the control and management of the utilities of such city shall provide for the payment of such bonds by fixing rates, fees or charges for the use of or services rendered by such utility, which rates, fees or charges shall be sufficient to pay the cost of operation, improvement and maintenance of the utility and pay the principal of and the interest upon such bonds when due.

(b) The city shall cause an audit to be made annually by a licensed municipal public accountant or certified public accountant of the operation of any utility for which revenue bonds have been issued by the city. If the audit discloses that proper provision has not been made for all of the requirements of this section, then the governing body or other officers having the control and management of the water and sewage system of such city shall promptly proceed to cause to be charged for the utility service rendered rates which will adequately provide for the requirements of this section. Within one year after the end of the audit period of the audit, a copy of the audit report shall be filed with the clerk of the city and shall be open to public inspection.