(1) If a person described in section 5(1)(d) later becomes a member of this retirement system, service credit shall not be given for employment that is excluded in that subdivision for purposes of determining a retirement allowance.

  (2) If a person described in section 5(1)(b) later becomes a member of this retirement system within 12 months after the date of termination as a participant in a transitional public employment program, service credit shall be given for employment that is excluded in section 5(1)(b) for purposes of determining a retirement allowance upon the payment by the person’s employer under the transitional public employment program from funds provided under the former comprehensive employment and training act of 1973, Public Law 93-203, as funds permit, to the retirement system of the contributions, plus regular interest, the employer would have paid had the employment been rendered in a position covered by this act. During the person’s employment in the transitional public employment program, the person’s employer shall place in reserve a reasonable but not necessarily an actuarially determined amount equal to the contributions that the employer would have paid to the retirement system for those employees in the transitional public employment program as if they were members under this act, but only for that number of employees that the employer determines would transfer from the transitional public employment program into positions covered by this act. If the funds provided under the former comprehensive employment and training act of 1973, Public Law 93-203, are insufficient, the remainder of the employer contributions shall be paid by the person’s employer under the transitional public employment program. If a person was not employed by a reporting unit but performed services for that reporting unit under a transitional public employment program and became a member of this retirement system within 12 months after the date of termination as a participant in the transitional public employment program, service credit shall be given for that transitional public employment program service in the manner provided in this subsection. The reporting unit for which the transitional public employment program service was performed is the person’s employer under the transitional public employment program for the purposes of this subsection.

  (3) Before January 31, 1991, a person excluded from membership as provided by section 5(1)(a) who later becomes a member of this retirement system shall be entitled to purchase service credit for that service, as provided in subsection (6), upon presenting acceptable proof of the service for the excluded period.

  (4) Before January 31, 1991, a member of the retirement system with employment excluded from membership service under section 5(1)(c) or under section 23a(1)(c) of chapter I or section 12(2)(c) of chapter II of former Act No. 136 of the Public Acts of 1945 shall be entitled to purchase service credit for that employment, as provided in subsection (6), upon presentation of documentation of the employment rendered that is verified from official reporting unit records or other acceptable documentation as determined by the retirement board. This subsection only applies after June 30, 1987 if the employment being purchased was performed while the person was enrolled as a graduate student at the reporting unit and the employment consisted of 1 or more of the following:

  (a) Teaching.

  (b) Research.

  (c) Academic advising.

  (d) Administration.

  (e) Library work.

  (f) Other employment of an academic or educational nature, as determined by the board.

  (5) Before January 31, 1991, a member of the retirement system with out of system public education service or with service described in section 69c(1) that was performed while the person was a full-time student, whether performed before, on, or after October 31, 1980, shall be entitled to purchase service credit for that service, as provided in subsection (6), upon presentation of documentation of the service rendered that is verified from official payroll records or other acceptable documentation as determined by the retirement board pursuant to R 38.1119 of the Michigan administrative code. This subsection only applies after June 30, 1987 if the employment being purchased was performed while the person was enrolled as a graduate student at a public college or public university and the employment consisted of 1 or more of the following:

  (a) Teaching.

  (b) Research.

  (c) Academic advising.

  (d) Administration.

  (e) Library work.

  (f) Other employment of an academic or educational nature, as determined by the board.

  (6) Service credit shall not be given under subsection (3), (4), or (5) until the member pays into the retirement system the actuarial cost. Service credit shall not be given under subsection (3), (4), or (5) unless the service being purchased is followed by 5 years of reporting unit service credit under this act or former Act No. 136 of the Public Acts of 1945. Credit provided by subsection (3), (4), or (5) shall not be used in satisfying the minimum of 10 years of service credit required under this act for a retirement allowance.

  (7) A person excluded from membership as provided by section 5(1)(f), (g), (h), (i), (j), or (k) shall not receive service credit for the employment described in those subdivisions even if the person subsequently becomes or has been a member of this retirement system.