The city council of a city of the metropolitan class shall annually or biennially appropriate money and credits of the city in such amounts as may be deemed necessary and proper and set such money and credits aside to the following designated funds to be known as statutory funds: (1) For the fire department of the city, (2) for the police department of the city, (3) for the public library, and (4) for the purpose of paying judgments and costs. The amounts so appropriated and set aside to such funds respectively shall be the maximum amounts that may be appropriated to or expended from such funds within the fiscal year or biennial period for the purposes for which such funds respectively are created.