“Final compensation” for members whose service is on a tenure which is temporary, seasonal, intermittent, or for part time only means one-third of the total compensation earned for that period of time during which the member rendered the equivalent of three years of full-time service.
The member may elect at or before the time he files an application for retirement the period of time during which he has earned three full years of credit upon which final compensation shall be calculated. If he does not so elect, such period of time immediately preceding his retirement shall be used.