There is a short cut for this, as the work is the same as that required to lift a

point mass equal to that of the rope from a position coincident with the

centre of mass of the rope to the top of the building. This is also equal to

the change in potential energy of the system so is:

W = mgh,

here m = 0.35*40 = 14 pounds, g= 32 ft/s^2, and h = 20 ft, so:

W = 8960 ft poundals (or 280 ft pounds)

RonL