(a) A member shall become eligible to receive a service pension, after the member has terminated employment, beginning with the month when:
(1) The member has 5 years of credited service and has attained age 62; or
(2) The member's age plus credited service (but not less than 10 years) equals 75; or
(3) The member has 5 years of credited service, and has retired under the provisions of § 8811 of this title; or
(4) The member has 20 years of credited service.
(b) An inactive member with a vested right to a service pension shall become eligible to receive such pension, computed in accordance with the provisions of this chapter in effect when the member ceased to be an employee, beginning with the first month after attainment of age 62.
(c) For purposes of this section, credited service shall include any period during which a member is receiving a disability pension as provided by this chapter.