Whenever anyone is convicted of an offense under any section of this penal code, or section of any other city ordinance, in addition to the fine imposed he must pay the costs of prosecution. In default of such payment, he shall be imprisoned until such fine is paid or worked out on the basis of eighteen dollars and fifty cents per each day of imprisonment, or he shall be required to do labor as directed by the court for the city to work out the fine on the basis of two dollars per hour for such labor. (Ord. 628, 1976)