Harry, who has a mass of 54 kg, has just gotten a flybar pogo stick and is standing on top of a small wall. He pushes off the wall with a velocity of 1.7 m/s, gets on the stick and lands. The stick has a spring constant of 3.5 x 104 N/m and he compresses it by 20.0 cm when he lands on the ground. How high was the wall he was standing on?