(1) A member annuity which shall be the actuarial equivalent of the member's accumulated contributions at retirement, plus a state annuity which, when added to the member annuity, shall be equal to:

(A) In the case of a member in Group 1, one and one-half percent (1.5%) of the member's average final compensation, multiplied by the number of years of creditable service, plus one fourth of one percent (0.25%) of the member's average final compensation in excess of the social security integration level applicable at the time of retirement, multiplied by the number of years of the member's creditable service;

(B) In the case of a member in Group 2, one and three-fourths percent (1.75%) of the member's average final compensation, multiplied by the number of years of creditable service plus one half of one percent (0.5%) of the member's average final compensation in excess of the social security integration level applicable at the time of retirement, multiplied by the number of years of creditable service plus one half of one percent (0.5%) of the average final compensation not in excess of the social security integration level, multiplied by four-tenths of one percent (0.4%) for each month which the member's age is less than sixty-five (65) years of age, multiplied by years of service;

(C) In the case of a member in Group 3, two percent (2%) of the member's average final compensation, multiplied by the number of years of creditable service plus one half of one percent (0.5%) of the member's average final compensation in excess of the social security integration level applicable at the time of retirement, multiplied by the number of years of creditable service, plus one half of one percent (0.5%) of the average final compensation not in excess of the social security integration level, multiplied by four tenths of one percent (0.4%) for each month which the member's age is less than sixty-five (65) years of age, multiplied by years of service;

(D) In the case of a member in Group 4, two and one-half percent (2.5%) of the member's average final compensation, multiplied by the number of years of creditable service.

(2) However, in the case of a member who at the time of retirement has not accumulated sufficient quarters of coverage under the Social Security Act (42 U.S.C. § 301 et seq.), to qualify for social security benefits at sixty-five (65) years of age, the member's annuity plus the state annuity shall equal:

(A) In the case of a member in Group 1, one and three-fourths percent (1.75%) of the member's average final compensation, multiplied by the number of years of creditable service;

(B) In the case of a member in Group 2, two and one-fourth percent (2.25%) of the member's average final compensation, multiplied by the number of years of creditable service; or

(C) In the case of a member in Group 3, two and one-half percent (2.5%) of the member's average final compensation, multiplied by the number of years of creditable service.