Sec. 14B. CONTRIBUTION DECREASES. (a) If at any time a qualified actuary that meets the requirements of Section 10A(b)(1) of this Act determines that the total contribution rate, expressed as a percentage of wages, is sufficient to amortize the unfunded actuarial accrued liability, as defined under the Governmental Accounting Standards Board Statement No. 25, over a 25-year period:

(1) the city's or town's governing body may decrease the city or town contribution rate; and

(2) to the extent that the city or town contribution rate decreases under Subdivision (1) of this subsection, the member contribution rate must decrease by an amount equal to the member contribution rate before the decrease multiplied by a fraction:

(A) the numerator of which is the decrease in the amount of the city or town contribution rate; and

(B) the denominator of which is the amount of the city or town contribution rate before the decrease.

(b) The sum of the city or town contribution rate and the member contribution rate after a decrease under this section may not be less than the total contribution rate determined by the qualified actuary to be necessary to amortize the unfunded actuarial accrued liability over a 25-year period.