Notwithstanding the provisions of Kan. Stat. Ann. §§ 74-4911 and 74-4913 to the contrary, any employee of a participating employer with an entry date of January 1, 1962, who became a member of the Kansas public employees retirement system on February 1, 1970, who was first employed by said participating employer on January 14, 1957, and who is employed by a participating employer on the effective date of this act, shall upon the payment of appropriate employer and employee contributions, be entitled to receive participating service credit for employment with his participating employer for the period January 1, 1962, until January 31, 1970. Said employee shall also be granted prior service credit from January 14, 1957, until December 31, 1961. The prior service benefit shall be computed by using a prior service annual salary of three thousand one hundred twenty-eight dollars and twenty-eight cents ($3,128.28).