Part A: $225 is her monthly payment.
Part B: She will have paid $20,325.
Part A Explanation: 14,100 - 13,200 is 900. Then you divide 900 by 4. 4 being the months. When you divide that, You get, 225.
Part B Explanation: You have the $6000 dollar down payment, plus the $14,225 total is payments. It equals 20,325.
Hope this helps!