The officers of a cooperative shall consist of a president, vice-president, secretary and treasurer who shall be elected annually by and from the board of trustees. No person shall continue to hold any of the above offices after he shall have ceased to be a trustee. The offices of secretary and of treasurer may be held by the same person. The board of trustees may also elect or appoint such other officers, agents or employees as it shall deem necessary or advisable and shall prescribe the powers and duties thereof. Any officer may be removed from office and his successor elected in the manner prescribed in the bylaws.