Engineering and construction service provider, Simplex Projects debuted at Rs 323.75 on the National Stock Exchange (NSE), apremium of 75% over its offer price of Rs 185 a share on theback of positive sentiment and a strong market opening.Nearly 28 lakh shares of Simplex Projects changed hands in early trades on the NSE. At 1030hrs, the scrip was trading at Rs 277.45 a share.Simplex Projects had come out with an initial public offer (IPO) of 30lakh equity shares, priced in a band of Rs 170 to Rs 185 a share.Overall the issue had been subscribed about 85 times.