A child in a wheelchair (total mass 56.5 kilogram) wins a race with a skateboarder. He has speed 1.40 m/s at the crest of a slope 2.25 meter high and 12.4 meter long. At the bottom of the slope his speed is 6.90 m/s. If air resistance and rolling resistance can be modeled as a constant friction force of 41.0 Newton, determine the work he did in pushing forward on his wheels during the downhill ride.