A partially amortizing FRM loan with the following term is being made:

A partially amortizing FRM loan with the following term is being made: Fixed rate with 3 discount point charges, constant payment, 12% interest rate for 20 year, $100,000 mortgage amount with a balloon payment of $50,000 schedule at the end of 20 years. The borrow will prepay at the end of 5 year with one percent of prepayment. What is the effective rate of interest.P/s: please help me show work by using financial calculator. Tks!