The city council shall annually provide for an outside audit of the books and accounts of the city to be conducted by a certified public accountant or a firm of certified public accountants, which has no personal interest, direct or indirect, in the fiscal affairs of the city or any of its officers. The mayor shall annually provide to the city council a sum of money sufficient to satisfy the estimated cost of conducting the audit as presented to the mayor, in writing, by the city council. The award of a contract to audit shall be made by the city council on or before September 15 of each year. The clerk of the council shall coordinate the work of the individual or firm selected. The report of the audit shall be filed in final form with the city council not later than March 1 in the year following its award.