Opening Capital = Closing Capital - Profit + Drawings - Additional Capital = 12,00,000 - 3,00,000 + 1,00,000 - 5,00,000 = 5,00,000. Interest on opening capital for full year = 5,00,000 x 12% = 60,000. Interest on additional capital (6 months) = 5,00,000 x 12% x 6/12 = 30,000. Total = Rs. 90,000.