What sum invested at 4% per annum compounded semi-annually amounts to ₹7803 at the end of one year?

A man invests ₹1200 for two years at compound interest. After one year the money amounts to ₹1275. Find the interest for the second year correct to the nearest rupee.

At what rate percent per annum compound interest will ₹2304 amount to ₹2500 in 2 years?