A tennis ball of mass 0.0611 kg is served. It strikes the ground with a velocity of 55.6 m/s (124 mi/h) at an angle of 21.2° below the horizontal. Just after the bounce it is moving at 54.6 m/s at an angle of 17.1° above the horizontal. If the interaction with the ground lasts 0.0728 s, what average force did the ground exert on the ball?