(a) The board shall designate:
(1) the number of districts; and
(2) the geographic area of a district composed of various counties.
(b) The board may revise, as it considers appropriate and after a public hearing, the number of districts and the designation of the counties located in a district.
(c) If the number of districts or a county's designation in a district is revised, the board shall follow the same procedure that applied to the initial designation.