A ball is kicked with an initial velocity of 21 m/s in the horizontal direction and 16 m/s in the vertical direction. (Assume the ball is kicked from the ground. For each answer, enter a number.) (a) At what speed (in m/s) does the ball hit the ground? m/s (b) For how long (in s) does the ball remain in the air? S (c) What maximum height (in m) is attained by the ball? m +