Physics Help? C4:4

Question

A 100-kg athlete is performing a vertical leap to test his leg strength.  He leaves the ground at 3.20 m/s, zooms upward to some maximum altitude, and then returns to the ground.  As he lands, he bends his legs and crouches down, so that he moves 30 cm downward as he comes to a stop.

 

4)         What average force did the athlete’s legs exert on the ground as he landed?