Sec. 9. (a) Except as provided in subsection (b), every participant is required to retire on the first day of the month following the participant's sixty-fifth birthday.
(b) An officer who becomes a participant after becoming fifty (50) years of age is required to retire on the earlier of:
(1) the first day of the month following the participant's sixty-fifth birthday; or
(2) the first day of the month following the completion of fifteen (15) years of service.