Which situation(s) could by modeled by a linear function?

I. You have an assignment due and your teacher deducts 2 points for each day the assignment is turned in after the due date.

II. A car depreciates at a rate of 15% per year.

III. A bicyclist travels at a constant rate of 25 miles per hour for 30 minutes. She stops for 10 minutes and then travels at a constant rate of 30 miles per hour for 15 minutes.

O I only

O II only

O III only

O I and III only