A composite beam is constructed by bolting lour plates to lour 60 X 60 X 12- mm angles as...

A composite beam is constructed by bolting lour plates to lour 60 X 60 X 12- mm angles as shown. The bolts are equally spaced along the beam, and the beam supports a vertical load. As proved in mechanics of materials, the shearing forces exerted on the bolts at Aand Bare proportional to the first moments with respect to the centroidal xaxis of the red shaded areas shown, respectively, in parts aand bof the figure. Knowing that the force exerted on the bolt at Ais 280 N. determine the force exerted on the boft at B.