The steel frame (E=200GPa) shown has a diagonal brace BD with an area of 1920mm^2. Determine the largest allowable load P if the change in length of member BD is not to exceed 1.6 mm. Bottom left of frame is A, top left is B, top right is C and bottom right is D. Length AD=5m, length AB=6m. P is Horizontal and applied to C of the frame.