Problem 6.2-4.a A round steel tube of outside diameter d₂ and a brass core of diameter d₁ are bonded to form a composite beam, as shown in the figure. Derive formulas for the allowable bending moment M that can be carried by the beam based upon an allowable stress σ, in the steel and an allowable stress σg in the brass. (Assume that the moduli of elasticity for the steel and brass are E, and EB, respectively.) S B d2 PROB. 6.2-4