(1) Unless the articles of incorporation provide otherwise, if a vacancy occurs on a board of directors, including a vacancy resulting from an increase in the number of directors:

(a) The shareholders may fill the vacancy;

(b) The board of directors may fill the vacancy; or

(c) If the directors in office constitute fewer than a quorum of the board, they may fill the vacancy by the affirmative vote of a majority of all the directors in office.

(2) If the vacant office was held by a director elected by a voting group of shareholders, only the holders of shares of that voting group are entitled to vote to fill the vacancy, if it is filled by the shareholders, and only the directors elected by that voting group are entitled to fill the vacancy if it is filled by the directors.

(3) A vacancy that will occur at a specific later date, by reason of a resignation effective at a later date under RCW 23B.08.070(2) or otherwise, may be filled before the vacancy occurs but the new director may not take office until the vacancy occurs.