The compound wooden beam is connected together by at bolt at b. assuming that the connections at a, b, c. and d exert only vertical forces on the beam, determine the required diameter of the bolt at b and the required outer diameter of its washers if the allowable tensile stress for the bolt is (sigma t)allow = 150 mpa and the allowable bearing stress for the wood is (sigma b)allow = 28mpa. assume that the hole in the washers has the same diameter as the bolt.