Gere & Goodno — Stresses in Beams (Advanced Topics): Problem R-6.2

R-6.2 A composite beam is made up of a 90 mm × 160 mm wood beam (\(E_w = 11 \text{ GPa}\)) and a steel bottom cover plate (90 mm × 8 mm, \(E_s = 190 \text{ GPa}\)). Allowable stresses in wood and steel are 6.5 MPa and 110 MPa, respectively. The allowable bending moment about the \(z\) axis of the composite beam is most nearly: (A) 2.9 kN·m (B) 3.5 kN·m (C) 4.3 kN·m (D) 9.9 kN·m