Goa Carbon - part of the Rs 1,000 crore Dempo group and the second largest manufacturer of calcined petroleum coke in the country - has filed a draft letter of offer with Sebi for its rights issue in the ratio of 1:1.According to a release issued by the company today, the rights issue to existing shareholders is for 46 lakh shares of Rs 10 each at a premium of Rs 70 per share aggregating Rs 36.80 crore.On completion of the rights issue, the equity of Goa Carbon will go up to 92 lakh shares of Rs 10 each. The promoter group holds 56.16 per cent of the equity."We plan to repay our term debt as well as part of our working capital through the rights issue, which will result in significant savings in interest costs," Shrinivas Dempo, executive chairman of Goa Carbon, said.