A bicycle tire is spinning clockwise at 2.10 rad/s. During a time period t = 2.40 s, the tire is stopped and spun in the opposite (counterclockwise) direction, also at 2.10 rad/s. Calculate the change in the tire's angular velocity and the tire's average angular acceleration _av. (Indicate the direction with the signs of your answer

(a)the change in the tire's angular velocity (in rad/s)

(b)the tire's average angular acceleration _av (in rad/s²)