(a) Revenue refunding bonds may:
(1) be combined with new or original revenue bonds into one series or issue;
(2) be issued to refund bonds of more than one series or issue;
(3) combine the pledges securing the bonds to be refunded to secure the revenue refunding bonds; or
(4) be secured by a pledge of other or additional net revenue.
(b) Revenue refunding bonds may bear interest at a rate higher than that of the bonds to be refunded.