Answer:
42 ft/s
Explanation:
The change in velocity is given by the area under the curve from t=0 to t=6. The average acceleration over that period is (10+4)/2 = 7 ft/s^2, so the change in velocity is ...
(7 ft/s^2)(6 s) = 42 ft/s
The velocity of the car at t=6 is 42 ft/s.