Benefit rates. Commencing and ending dates.

(b) Proratable retirement. The proratable retirement benefit shall be computed as follows: Average annual salary multiplied by (1) number of years of credited service in the public schools of Connecticut multiplied by the applicable percentage based on age and service as determined from the table below, and (2) number of years of all additional credited service not used in subdivision (1) of this subsection multiplied by one per cent. TABLE AGE OF RETIREMENT