(a) At the time general obligation bonds are issued under Section 1117.251, the board shall impose an ad valorem tax at a rate sufficient to create an interest and sinking fund and to pay the principal of and interest on the bonds as the bonds mature.
(b) The tax required by this section together with any other tax imposed for the district may not in any year exceed 75 cents on each $100 valuation of taxable property in the district.