Fords recent commercials advertise $750 cash back and 0.9% APR financing for 48 months or just $1,500 cash back on an Escort or ZX2. Lets assume Suzie wants to buy the ZX2, which costs $15,000 and she has no down payment other than the cash back from Ford. If she chooses the $1,500 cash back, Suzie can borrow from the National City Bank at 7.9% APR for 48 months. What will Suzies monthly payment be under each option? Which option should she choose?

To make the two options indifferent to her, how lower or higher should the interest rate Suzie pays to the National City Bank be?