you are in the process of purchasing a new automobile that will cost you $27,500. the dealership is offering you either a $2,500 rebate (applied toward the purchase price) or 1.9% financing for 48 months (with payments made at the end of the month). you have been preapproved for an auto loan through your local credit union at an interest rate of 3.9% for 48 months. should you (a) take the $2,500 rebate and finance through your credit union or (b) forgo the rebate and finance through the dealership at the lower 1.9% apr?