Sec. 4.021. CONTRIBUTIONS BY A MUNICIPALITY. (a) Subject to Section 4.022 of this Act, a municipality to which this Act applies shall pay into the fund on each payroll date the municipal contribution amount applicable to the fiscal year in which the payroll date occurs. The municipal contribution amount applicable to a fiscal year equals the amount obtained by:

(1) multiplying the average member salary for the preceding fiscal year by the percentage equal to 100 percent plus the estimated percentage increase in the annual member payroll from the preceding fiscal year to the fiscal year as determined by the actuary;

(2) multiplying the product computed under Subdivision (1) of this subsection by 9.4 percent;

(3) dividing the product computed under Subdivision (2) of this subsection by the total number of payroll dates that occur during the fiscal year; and

(4) multiplying the quotient computed under Subdivision (3) of this subsection by the number of individuals who are members on the payroll date.

(b) The municipal contributions to and health benefits paid from the fund are part of the compensation for services rendered to the municipality. This Act is considered part of the contract of employment and appointment of the firefighters and police officers of that municipality.