Answer:
a. In order to determine the present value of lease we can use the same APR as the car loan (7%). We can use the present value of an annuity formula:
PV = monthly payment x annuity factor
PV of the annuity = $509 x 41.76344 = $21,257.59
total present value of lease contract = $21,257.59 + $109 = $21,366.59
b. the present value of purchasing the car is $40,000 - $28,000/1.07⁴ = $40,000 - $21,361.07 = $18,638.93
c. the break even resale price = (sales price - PV of lease) x (1 + 7%/12)⁴⁸ = ($40,000 - $21,366.59) x (1 + 0.07/12)⁴⁸ = $18,633.41 x 1.32205 = $24,634.37