The compensation for each director per day while performing duties as a member of the board must be fixed by the board of directors but may be no more than sixty-two dollars and fifty cents per day. The allowance for meals and lodging expenses must be at the same rate and under the same conditions as provided for state officials and employees. The allowance for travel expenses must be at the same rate as provided by section 11-10-15 and must be     evidenced by a subvoucher or receipt in a manner determined by the board of directors. The salary of the secretary, assessor, and treasurer must be determined by the board of directors.