A hardening spring applies a non constant force F = .12(x + 10x2) lb to block A. A = 4.8 lb, B = 23 lb and B is 18 inches above the floor. The large pulley has a mass of .125 slug and a radius of 6 in. The two smaller pulleys have identical masses of .031 sl and radii of 2 in. All pulleys are thin disks. What is the speed of (a) B and (b) A just before B hits the floor? Ignore friction.