This is the 3rd time I am posting the question, no one answered.

A wet solid is dried in a trayed batch dryer under constant drying conditions. The total drying time required to reduce the moisture content of the solid from X1=0.26 (kg H2O/kg dry solid) to X2=0.06 is 8 hours. The decreasing flow period of the solid is a line passing through the origin and is given by the function R=X. a-) Find the total time required for the moisture content of the wet solid to decrease from X1=0.33 (kg H2O/kg dry solid) to X2=0.03 . (The critical free moisture content of the solid is Xc=0.14.) b-) Considering the variation of the drying rate in the decreasing flow period, write down what kind of material this wet solid might belong to.