A 180-lb man carries a 5-lb can of paint up a helical staircase that encircles a silo with radius 20 ft. The silo is 80 ft high and the man makes exactly two complete revolutions. Suppose there is a hole in the can of paint and 4 lb of paint leaks steadily out of the can during the man's ascent. How much work is done by the man against gravity in climbing to the top?