a chain hangs over a pulley from the top of a building 200 feet tall. the chain is 300 feet long, so initially 100 feet of chain lies on the ground. the chain weighs 3/2 pounds per foot. how much work is required to roll up all of the chain to the top of the building? hint: you may want to break the problem into parts where one part is when there is still chain on the ground and the second part is when the chain is off the ground.