Sec. 14. (a) Interest shall be credited at least annually on or before June 30 at a rate specified by rule by the board on all amounts credited to the member as of June 30 of the preceding year.
(b) Contributions begin to accumulate interest at the beginning of the fiscal year after the year in which the contributions are due.
(c) When a member retires or withdraws, a proportional interest credit determined under this chapter shall be paid for the period elapsed since the last date on which interest was credited.