A boy in a wheelchair (total mass 45 kilogram) has speed 1.40 meter per second at the crest of a slope 2.20 meter high and 12.4 meter long. At the bottom of the slope his speed is 6.90 meter per second. Suppose air resistance and rolling resistance can be modeled as a constant friction force of 41 N. Obtain the work he did in pushing forward on his wheels during the downhill ride.