Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4902 to the contrary, an employee who became a member of the Kansas public employees retirement system on January 1, 1971, and who was employed with a non-participating employer from May 1, 1965, until December 31, 1969, may elect to purchase credit for such service by means of a lump sum payment equal to four percent (4%) of the compensation such member received during such period from the non-participating employer. If such election and payment is made by the member, the member’s present participating employer shall pay an amount equal to the employer contributions which would have been made during such period. Such election and payment must be made within six (6) months of the effective date of this act.