The 80-lb boy stands on the beam and pulls on the cord with a force large enough to just c...

The 80-lb boy stands on the beam and pulls on the cord with a force large enough to just cause him to slip. If (μs)D = 0.4 between his shoes and the beam, determine the reactions at A and B. The beam is uniform and has a weight of 100 lb. Neglect the size of the pulleys and the thickness of the beam.