(1) Class A: (i) one and one-eighth per cent (1⅛%) of his average compensation multiplied by the total number of years of his creditable service, plus an additional five-eighths of one per cent (⅝%) of the part of such compensation in excess of four thousand two hundred dollars ($4,200) multiplied by the number of years of his creditable service rendered prior to July 1, 1963, plus an additional five-eighths of one per cent (⅝%) of the part of such compensation in excess of four thousand eight hundred dollars ($4,800) multiplied by the number of years of his creditable service rendered after July 1, 1963, and prior to January 1, 1966, plus an additional allowance for each year of creditable service rendered after January 1, 1966, equal to five-eighths of one per cent (⅝%) of the part of such compensation in excess of covered compensation applicable to such year, or (ii) if the member's service retirement date occurs before his sixty-fifth (65th) birthday, his retirement allowance as computed in (i) above shall be permanently reduced by four-tenths (4/10) of one per cent (1%) for each full month the member retires prior to his attaining age sixty-five (65).

(2) Class B: (a) one and three-quarters per cent (1¾%) of his average compensation multiplied by the total number of years of his creditable service plus (b) for a member who elects, pursuant to § 8-3431(2), to make additional contributions, after July 1, 1967, an additional allowance equal to one and three-quarters per cent (1¾%) of his average excess compensation multiplied by the number of years of his creditable service rendered after July 1, 1967, plus the number of years of creditable service rendered prior to July 1, 1967, provided the member made additional contributions on the part of earned compensation in excess of the maximum rate thereof. “Average excess compensation,” as used herein, means the excess of the arithmetic average of the member's earned compensation, without limit as to a maximum rate of earned compensation, over his average compensation as computed in accordance with § 8-3401(n).

(3) Class C: two and one-fourth per cent (2¼%) of his average compensation multiplied by the total number of years of his creditable service.

(c) Retirement allowance, determined in accordance with this section;

(d) Primary social security, determined in accordance with the social security law as of the date for which total benefit is being determined and shall be exclusive of benefits on account of a spouse or of any other member of the family.