(1) A member, upon retirement from service, shall receive a retirement allowance subject to the provisions of paragraph (2) of this section, which shall consist of:
(a) An annuity which shall be the actuarial equivalent of his or her accumulated contributions at the time of his or her retirement.
(b) A pension purchased by the contributions of the city, equal to the annuity purchased by the accumulated normal contributions of the member.
(c) For any member having credit for prior service an additional pension, purchased by the contributions of the city equal to one and one-third percent of the final compensation, multiplied by the number of years of prior service credited to said member, except that if a member shall retire before attaining the age of sixty-two years, the additional pension shall be reduced to an amount which shall be equal to a lesser percentage of final compensation, multiplied by the number of years of prior service credited to said member, which lesser percentage shall be applied to the respective ages of retirement in accordance with the following tabulation:
(3) Any member, who enters the retirement system on July 1, 1939, or who enters after that date and who is given the credit for prior service, and who is retired by reason of attaining the age of seventy years, shall receive such additional pension on account of prior service, purchased by the contributions of the city, as will make his or her total retirement allowance not less than four hundred twenty dollars per year.
(4) Any member who, at the time of his or her retirement, has at least ten years of creditable service, as defined in this chapter, and who has attained the age of sixty-five years or over, shall receive such additional pension, purchased by the contributions of the city, as will make his or her total retirement allowance not less than nine hundred sixty dollars per year.