(a) If a district issues refunding bonds, the district shall annually levy taxes on all taxable property in the district sufficient to pay interest on the bonds as it becomes due and to pay the principal of the bonds at maturity.
(b) In making the annual levies, the district may take into consideration estimated delinquencies based on tax collection experience over the preceding years and levy the taxes in an amount, after deduction of estimated delinquencies, sufficient to pay principal and interest requirements and the cost of tax collection.

(c) In its discretion and so far as consistent with the rights of the holders of the bonds refunded, a district may pledge to the payment of the refunding bonds the proceeds of taxes levied for payment of the bonds refunded and delinquent at the time of the authorization of the refunding bonds, cash or securities in the sinking fund maintained for payment of the bonds refunded, or both.