Simple interest on a sum of money, at 5% per annum for 2 years, is ₹50. The compound interest on the same sum for the same period at the same interest rate is:
A sum of ₹800 is invested for 3 years at simple interest rate. The rates of interest for the 3 years are 6%, 8% and 10% per annum. Find the total amount of interest earned at the end of 3 years.