Where M/s. Garden Reach Shipbuilders and Engneers Limited, Kolkata (hereinafter referred to as GRSE), makes sales, on or after the 1st day of April, 2005, to Indian Navy, Government of India, Ministry of Defence, of vessel constructed by it on the basis of cost plus remuneration contract, the GRSE may, for the purpose of determination of his taxable turnover of sales on which tax is payable, deduct under clause (c) of sub-section (1) of section 16 from its gross turnover of sales that part of such gross turnover which represents sales of such vessel.