Adog runs in a straight line along the x-axis to retrieve a thrown toy. the dog starts from rest at x = 0 at time t = 0, runs to x = +15.0 m and comes momentarily to rest there at t = 4.0 s, turns around and runs back past x = 0 at time t = 7.5 s, and finally comes to rest again at x = -10.0 m at t = 10.0 s. in order to start and stop moving at appropriate points, the dog accelerates smoothly as necessary. in answering these questions, it may if you draw a sketch of the situation, marking the dog's position at various times. what is the dog's displacement (in m) for the entire trip?