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