20 102 kg hot-air balloon takes off from rest at the surface of the earth. The nonconservative wind and lift forces take the balloon up, doing +9.70...

A 4.20 102 kg hot-air balloon takes off from rest at the surface of the earth. The nonconservative wind and lift forces take the balloon up, doing +9.70 104 J of work on the balloon in the process. At what height above the surface of the earth does the balloon have a speed of 7.30 m/s?