(b) The number of directors may be increased or decreased by amendment of the by-laws, or by action of the shareholders or of the board under the specific provisions of a by-law adopted by the shareholders, subject to the following limitations:

1. (1) If the board is authorized by the by-laws to change the number of directors, whether by amending the by-laws or by taking action under the specific provisions of a by-law adopted by the shareholders, such amendment or action shall require the vote of a majority of the entire board.
2. (2) No decrease shall shorten the term of any incumbent director.