A fibrous material in the form of sheets 4 ft x 8 ft x 1 in thick is dried in a countercurrent adiabatic tunnel dryer. The sheets are transported in racks that transport 20 sheets spaced 4 inches apart. so that drying occurs on both sides. 5 lb of air at 260F and 105F Tw enters the dryer for each pound of dry solid and flows around it at the rate of 800 lb/hft2 of free air. The solid enters at 80F with a moisture of 0.80 lb H2O/lbds(pounds of dry solid) and leaves the dryer with a moisture content of 0.04 lb H2O/lbds and 200F. The solid has a bulk density of 40 lbds/ft3 and a heat capacity of 0.3 cal/gC. Pilot tests indicate that the expected critical moisture is 0.25 lb H2O/lbds and that the equilibrium moisture content is negligible. Determine the required drying time and the air conditions at the outlet of the dryer