(a) Upon the written application to the board, any member of the system who (1) has attained age 65 and has completed eight or more years of creditable service or (2) has attained age 62 and has completed eight or more years of membership service shall be retired by the board on a retirement allowance and shall thereupon become a beneficiary of the system, provided that he is no longer in the service of the state, whether as a member of the General Assembly or otherwise. In lieu of eight years of service, a member may substitute four terms of office in the General Assembly.

(b) The effective date of retirement shall be the first day of the month in which the application is received by the board, but such effective date shall not, in any case, be earlier than the first day of the month following the final month of the applicant's employment. Applications for retirement shall not be accepted more than 90 days in advance of the effective date of retirement.

(c) Any member of the system who has completed eight or more years of membership service and who has attained age 60 may elect to retire prior to age 62, provided that in such event, his retirement allowance shall be reduced by 5 percent for each year below age 62.

(d) Upon such retirement under subsection (a) of this Code section, the retired member shall receive a monthly service retirement allowance which shall be equal to $28.00 multiplied by the number of years of the member's creditable service.

(e) Any increase in benefits payable under the retirement system which becomes effective as a result of a change in the benefit formula provided for by subsection (d) of this Code section shall be applicable to beneficiaries of the system who are receiving benefits at the time the increase becomes effective.

(f) Subject to the terms and limitations of this Code section, the board of trustees is authorized to adopt from time to time a method or methods of providing for increases in the retirement allowance provided in subsection (d) of this Code section for persons theretofore or thereafter retiring under this article. Such method shall be based upon:

(1) The recommendation of the actuary of the board of trustees;

(2) The maintenance of the actuarial soundness of the fund in accordance with the standards provided in Code Section 47-20-10 or such higher standards as may be adopted by the board; and

(3) Such other factors as the board deems relevant; provided, however, that any such increase shall be uniform and shall apply equally to all members of this retirement system.