(a) The number of directors constituting the entire board shall be not less than three. Subject to such limitation, such number may be fixed by the by-laws or by action of the members or of the board under the specific provisions of a by-law allowing such action, or by any number within a range set forth in the by-laws. If not otherwise fixed under this paragraph, the number shall be three.

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

(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, such amendment or action shall require the vote of a majority of the entire board.

(2) No decrease shall shorten the term of any incumbent director.