A rental car company offers two rental plans, Plan A and Plan B, for the same economy size car. For both plans, the total rental cost f(m) is a function of the number of miles m that the car is driven. Plan A: f(m) = 0.12m + 75
Plan B: f(m) = 0.35m

I. In complete sentences, translate each function into a verbal model describing the total cost of the rental in terms of the number of miles that the car is driven.
II. For each function, determine how the rate of change will affect the total cost of a rental car.
III. For a car rental that will include a maximum of 250 miles for the duration of the rental, which plan is the most cost effective?