The mayor and council shall cause the city's monies, other than sinking funds, to be deposited in any bank or banks in the city designated by said mayor and council, upon sufficient security, of the kind and character mentioned in the following section, to assure the safety of any such deposit or deposits, being given the city therefor by said bank or banks, said security to be approved by the mayor and council.
Said monies shall at all times be deposited in or with any such bank at the best obtainable rate of interest per annum on the daily balance of such deposits, to be computed monthly.