A 59.6-kg skateboarder starts out with a speed of 2.32 m/s. He does 115 J of work on himself by pushing with his feet against the ground. In addition, friction does -262 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 8.25 m/s. Calculate the change in the gravitational potential energy.