A batch of wet solid whose drying-rate curve is represented by Fig. is to be dried from a free moisture content of X1=0.38kgHH2O/kg dry solid to X2=0.04kgHH2O/kg dry solid. The weight of the dry solid is Ls=399kg dry solid and A=18.58m2 of top drying surlace. Calculate the time for drying. Note that Ls/A=399/18.58=21.5kg/m2