(a) Not later than the 90th day after a board vacancy for a district located in more than one county occurs, the remaining board members shall appoint a person to fill the unexpired term.
(b) If the board has not filled the vacancy before the 91st day after the date of the vacancy, the commissioners court of the county where the previous board member resided shall appoint a person to fill the vacancy.
(c) A person appointed under this section must be eligible to serve under Section 775.035.