The widow's annuity and widow's prior service annuity for the wife of an employee who (1) attained age 50 or more but less than age 63 while in service and (2) served 10 or more years and (3) withdraws from service, shall be fixed as of her age at the time of his withdrawal. The annuity, payable from and after the date of his death, shall be such amount as can be provided on a reversionary annuity basis from the following sums accumulated to his credit on the date the annuity was fixed:
40 ILCS 5/6-134