5. A teacher in the University of Ulster on 1st October 1984 who was employed in reckonable service as a teacher in the Ulster Polytechnic on 30th September 1984 unless he elected by notice in writing served on the Department not later than 30th September 1985, that service with the University of Ulster as from the date specified in the notice, not being later than 1st October 1985, should no longer be pensionable service.