(a) On final approval of the annual budget, the board shall impose a tax on all property in the district subject to district taxation.
(b) The tax may be used for all hospital district purposes mentioned in this chapter and in Section 11, Article IX, Texas Constitution, including to:
(1) pay the indebtedness issued or assumed by the district; and
(2) maintain and operate the district.
(c) The district may not impose a tax to pay the principal of or interest on revenue bonds.