A new employee charged $8520 on his credit card to relocate for his first job. After noticing that the interest rate for his balance was 21% compounded monthly, he stopped charging on that account. He wishes to pay off his balance in 3 years using automatic payments sent at the end of each month. a. What monthly payment must he make to pay off the account at the end of 3 years? b. How much total interest will he have paid? a. What monthly payment must he make to pay off the account at the end of 3 years? (Round to the nearest cent as needed.) b. How much total interest will he have paid? (Round to the nearest cent as needed.)