A careful analysis of the cost of operating an automobile was conducted by accounting manager Dia Bandaly. The following model was developed:

^{^}y = 4,000 + 0.20x

Where ^{^}y is the annual cost and x is the miles driven.
a) If the car is driven 15,000 miles this year, what is the forecasted cost of operating this automobile?
b) If the car is driven 25,000 miles this year, what is the forecasted cost of operating this automobile?