3) The monthly payment is $416.71, The total amount spent for the boat was $14,000 (down payment) + 48*$416.71 = $34,002.08
4) She had to pay the interest on the amount not paid for the first month = $634.9*(.2199/12) = $11.63
Then she has to pay the interest on the total of $634.90 + $712.18 = $1,347.08*(.2199/12) = $24.69
And she has to pay off the principal = $1,347.08
Total = $1,383.40
5) The monthly payment is $2,400.23
*Loan payment amounts calculated using the PMT function in EXCEL.