A Mathema A biker starts a trip and rides at a constant velocity of + 12 km/h for 0.20 h. For the next 0.10 h he bikes at an increased constant velocity and finds that he is at a rest stop +4.8 km from his starting point. In the next 0.20 h, half of which he rests, his average velocity is +9.0 km/h. a. Construct a d-t graph for the trip. b. What is his average velocity for the trip