(a) The board may impose an ad valorem tax within the maximum tax rate approved at the election for a purpose authorized by this subchapter if the tax is approved at an election held in the authority by a majority of the votes cast:
(1) throughout the authority; and
(2) in any three counties in the authority.
(b) The election must be ordered by ordinance of the board. The ordinance must include for each applicable county in the authority the polling places in that county where the election is to be held.