7. (09.01 MC)

A ball is thrown upward from the top of a building. The function below shows the height of the ball in relation to sea level, f(t), in feet, at different times, t, in seconds:

f(t) = −16t2 + 32t + 384

The average rate of change of f(t) from t = 3 seconds to t = 6 seconds is __
feet per second.