A 600 N volleyball player lands from a spike attempt and immediately jumps up to try for a block. When she first contacts the ground, her velocity is 3 m/s downward, and then as she leaves the ground for the block her velocity is 4 m/s upward. On the way down their center of gravity (COG) displaced 0.6 meters during the eccentric phase and on the way up the COG displaced 0.5 meters during the concentric phase. Calculate the work done and the average vertical GRF during both the eccentric phase (negative work) landing and the concentric phase (positive work) jumping.