3. A formwork system will be used to cast an elevated 8" thick, normal weight concrete slab. The construction live load is "medium duty" and the formwork is estimated to weigh 5 psf. Formwork sheathing will be 5/8" thick, Class I Plyform installed in the strong direction. a. Is a spacing of 20" for the joists structurally adequate? No need to design the entire slab formwork system. Just determine if the 20" plywood span is structurally sufficient to carry the load (check plywood bending, shear, and deflection at L/360). b. Regardless of whether the 20" spacing is adequate, should 20" spacing ever be used? Explain why or why not. c. What joist spacing would you specify in this design?