Each state employee who is a member of the state employees retirement system, part A, may, upon the enactment of and pursuant to federal-enabling legislation, elect to become a member of such retirement system, part B, and, from the date of such election, he shall pay his required Social Security contribution. If the federal-enabling legislation shall allow such employee to be covered by Social Security retroactively, such retroactive payment required to be paid by him as an employee shall be paid by the state to the federal government from the amount in the state employees retirement system standing to the credit of such employee and, if such amount is insufficient to make such payment, the deficiency shall be paid by such employee to the retirement system within the time and in the manner prescribed by the State Employees Retirement Commission. From the date of such election, provided any such deficiency has been paid, such employee shall be a part B member and be entitled, upon retirement, to the retirement benefits due to a member of the state employees retirement system, part B. Each member of the state employees retirement system who is employed by a state-aided institution, as defined in section 5-175, shall have an opportunity to elect to participate in part B of said system. Such election shall be made in the period between October 1, 1980, and December 31, 1980, in accordance with rules to be prescribed by the Retirement Commission.