(a) After bonds have been voted, the board shall levy a tax on all property in the district sufficient to pay the interest on the bonds together with an additional amount to be placed in the sinking fund to discharge and redeem the bonds at maturity, and the board shall annually levy or have assessed and collected taxes on all property in the district sufficient to pay for the expenses for assessing and collecting the taxes.
(b) The board may issue the bonds in serial form or to be paid in installments.

(c) The tax levy shall be sufficient to pay the interest on the bonds, to meet the proportional amount of the principal of the next maturing series of the bonds, and to pay expenses of assessing and collecting the taxes for the year.
(d) If a contract is entered into with the United States, the board shall levy a tax sufficient to meet all installments as they are due and to pay interest. The directors shall make an annual levy until the contracts and obligations are discharged.