You drive your car in a straight line at 15 m/s for 10 minutes, then at 25 m/s for another 10 minutes.

(a) Is your average speed for the entire trip greater than, less than, or equal to 20 m/s?

(b) Choose the best explanation from among the following:

I. More time is required to drive at 15 m/s than at 25 m/s.

II. Less distance is covered at 25 m/s than at 15 m/s.

III. Equal time is spent at 15 m/s and 25 m/s.