Starting at 48th Street, Dylan rides his bike due east on Meridian Road with the wind at his back. He rides for 20 min at 15 mph. He then stops for 5 min, turns around, and rides back to 48th Street; because of the headwind, his speed is only 10 mph.

a. How long does his trip take?

b. Assuming that the origin of his trip is at 48th Street, draw a position-versus-time graph for his trip.