The additional amount earned in the second year is the interest on the first year's interest, and the additional amount in the third year is the interest on the second year's interest. The compound interest rate is found by dividing the third year's additional interest by the second year's, so the rate is 2600.16 divided by 2418.75, which equals 1.0746 or 7.46%. The total interest in the third year is the second year's total interest plus 2600.16, and we find the second year's total interest by dividing 2418.75 by the interest rate of 0.0746 to get approximately 32435. Adding 2600.16 gives a third year total interest of approximately 35035. The fourth year interest will be 7.46% higher, so we multiply 35035 by 1.0746 to get Rs. 2,795.17.