Please answer the following question 15 and 17

​Q15. Vikram borrowed Rs. 20000 from a bank at 30% per annum simple interest. He lent it to his friend Venkat at the same rate but compounded annually. Find his gain after $2\frac{1}{2}\mathrm{years}$.

Q17. Mr Dubey borrows Rs. 100000 from State Bank of India at 11% per annum compound  interest. He repays Rs. 41000 at the end of first year and Rs.47700 at the end of second year.  Find the amount outstanding at the beginning of the third year.