The composite bar in Fig. P-247 is stress-free before the axial loads P1 and P2 are applied. Assuming that the walls are rigid, calculate the stress in each material if P = 150 kN and P = 90 kN. Aluminum A = 900 mm E = 70 GPa Steel A = 2000 mm E = 200 GPa Bronze A = 1200 mm E = 83 GPa P 500 mm 250 mm 350 mm Figure P-247 and P-248