The 12-ft-long walkway of a scaffold is made by screwing two 12-in. by 1/2-in. sheets of plywood to 1.5-in. by 3.5-in. timbers as shown. The screws have a 5-in. spacing along the length of the walkway. The working stress in bending is w = 850 psi for the plywood and the timbers, and the allowable shear force in each screw is F = 250 lb. What limit should be placed on the weight W of a person who walks across the plank? MARAAN 12 in. 3.5 in. 0.5 in. 1.5 in. FIG. P5.94 W 12 ft