§ 372. Optional retirement at age fifty-five; closed plan. a. Any member of the police and fire retirement system who, while a member of the state employees' retirement system, elected to contribute on a basis of retirement at age fifty-five pursuant to the provisions of section seventy-two of this chapter and who did not withdraw his or her election as therein provided shall contribute to the police and fire retirement system at the rate prescribed by such section, and if such member retires his or her retirement allowance shall be computed according to the provisions of such section.