The compound wooden beam is connected together by a 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 (σ_t)_allow = 150 MPa and the allowable bearing stress for the wood is (σ_b)_allow = 28 MPa. Assume that the hole in the washers has the same diameter as the bolt.