3. The rigid platform in the figure has negligible mass and rests on two steel bars, each 250.0 mm long. The center bar is Aluminum and 249.90 mm long. The initial gap between the rigid platform and the Aluminum bar is denoted by "A". Compute the stress in the Aluminum bar after the center load P = 400 kN has been applied. For each Steel bar, the area is 1200 sq.mm and E = = 200 GPa. For the Aluminum bar, the area is 2400 sq.mm and E = 70 GPa. Steel 400 kN A = 0.1 mm Aluminum Steel