When someone purchases a new car and begins to drive it, the mileage (meaning the number of miles the car has traveled) immediately increases. Let x represent the number of years since the car was purchased and y represent
the total miles traveled. The linear function that models the relationship between the number of years since
purchase and the total miles traveled is y = 15000x.

a. Identify and interpret the rate of change

b. Identify and interpret the initial value.