A heavy rope, 40 ft long, weighs 0.7 lb/ft and hangs over the edge of a building 90 ft high. (Let x be the distance in feet below the top of the building. Enter x,* as xj.) (a) How much work W is done in pulling the rope to the top of the building? Show how to approximate the required work by a Riemann sum. lim 7 xi x x 1 = 1 Express the work as an integral. 40 7 dx Evaluate the integral. 560 it- 1b (b) How much work W is done in pulling half the rope to the top of the building? How much work W is done in pulling half the rope to the top of the building? Show how to approximate the required work by a Riemann sum. 7 lim 20' x Ax Express the work as an integral. 20 7 20% X dx Evaluate the integral. 315 X ft-lb