(a) The member's monthly retirement benefit shall not change unless the Arkansas State Police Officers Deferred Option Plan receives a benefit increase.
(b)
(1) A member who participates in the plan shall earn interest at a rate set by the Board of Trustees of the State Police Retirement System that shall not be greater than the actuarially assumed investment rate of return for that time.
(2) The interest shall be credited to the individual account balance of the member on an annual basis.