Bill Anderson buys a car every 2 years as follows: initially he makes a down payment of $6000 on a $15,000 car. The balance is paid in 24 equal monthly payments with annual interest at 12%. When he has made the last payment on the loan, he trades in the 2-year-old car for $6000 on a new $15,000 car, and the cycle begins over again. Doug Jones decided on a different purchase plan. He thought he would be better off if he paid $15,000 cash for a new car. Then he would make a monthly deposit in a savings account so that, at the end of 2 years, he would have $9000 in the account. The $9000 plus the $6000 trade-in value of the car will allow Doug to replace his 2-year-old car by paying $9000 for a new one. The bank pays 6% interest, compounded quarterly.

(a) What is Bill Anderson's monthly payment to pay off the loan on the car?

(b) After he purchased the new car for cash, how much per month should Doug Jones deposit in his savings account to have enough money for the next car 2 years hence?

(c) Why is Doug's monthly savings account deposit smaller than Bill's payment?