[Forwarding of funds for payment of bonds and interest

coupons.] The secretary and treasurer of said regents shall forward to the bank at which said bonds are payable, prior to the date on which any coupons or principal of any of said bonds shall mature, out of the "interest and retirement fund" a sufficient sum of money to meet said coupons and maturing bonds as the same become due, plus any service charge which said bank shall be entitled to receive for its services.