Step-by-step explanation:
a) The displacement is the area under the curve.
Δx = ½ (10 s) (20 m/s) + (20 s) (20 m/s) + ½ (10 s) (20 m/s)
Δx = 600 m
b) The car is accelerating when the velocity is changing. This happens between t = 0 and t = 10, and between t = 30 and t = 40.
c) Average speed = displacement / time
v_avg = 600 m / 40 s
v_avg = 15 m/s