Sec. 10. NONSTATUTORY BENEFIT INCREASES. The benefits provided by this article may be increased if:

(1) an actuary selected by the board who, if an individual, is a Fellow of the Society of Actuaries, a Fellow of the Conference of Actuaries in Public Practice, or a member of the American Academy of Actuaries determines that the increase cannot reasonably be viewed as posing a material risk of jeopardizing the fund's ability to pay any existing benefit;

(2) a majority of the participating members of the fund vote for the increase by a secret ballot;

(3) the increase does not deprive a member, without the member's written consent, of a right to receive benefits that have already become fully vested and matured in a member; and

(4) the State Pension Review Board approves the determination by the actuary selected by the board that the increase cannot reasonably be viewed as posing a material risk of jeopardizing the fund's ability to pay any existing benefit.