(a) Service rendered by an employee as a police officer and member of the regularly constituted police department of the city, or as a firefighter and regular member of the paid fire department of the city, or as a teacher in the public school system in the city shall be counted, for the purposes of this Article, as service rendered as an employee of the city. Salary received for any such service shall be treated, for the purposes of this Article, as salary received for the performance of duty as an employee.
     (b) Credit shall be granted under subsection (a) only if (1) the employee pays to the Fund prior to his or her separation from service an amount equal to the employee contributions that would have been payable for that service, based on the salary actually received, plus interest at the effective rate, and (2) the employee has terminated any credit for that service earned in any other annuity and benefit fund or pension fund in operation in the city for the benefit of police officers, firefighters, or teachers. The amount transferred to the Fund under item (1) of Section 5-233.1, if any, shall be credited against the contributions required under this subsection.