The city treasurer may purchase certificates of deposit from and make time deposits in banks, capital stock financial institutions, or qualifying mutual financial institutions selected as depositories of city funds pursuant to sections 15-846 to 15-848. The certificates of deposit purchased and time deposits made shall bear interest and shall be secured as prescribed in such sections. The penal sum of such bond or the sum of such security shall be reduced in the amount of the time deposit or certificate of deposit insured or guaranteed by the Federal Deposit Insurance Corporation. Section 77-2366 shall apply to deposits in capital stock financial institutions. Section 77-2365.01 shall apply to deposits in qualifying mutual financial institutions.