(a) Where the bonds are payable both from taxes and from revenues of the district a tax shall be levied at the time of the authorization of the bonds sufficient to pay the principal and interest and create and maintain the reserve funds.
(b) The rate of tax actually to be collected for any year shall be fixed so as to take into consideration the money which shall have been in the interest and sinking fund from the pledged revenues and which will be available for payment of principal and interest and for the creation of the reserve funds to the extent and in the manner permitted by the resolution authorizing or the trust indenture securing the bonds.