mass transfer problem

8. Wet solid is air dried from 46% to 8.5% in a countercurrent continuous dryer. Air enters at 82C, absolute humidity 0.03kg water /kg dry air and discharged at same dry bulb temperature but absolute humidity 0.08kg water /kg dry air. The air rate is 1.36kg/m2s. Critical moisture is 50% and its percent equilibrium moisture is 1/4th of the percent relative humidity of air. Rate of drying is dX/dt=0.0137G1.47(XX)(YwY) Where Yw is saturation humidity of air at the wet bulb temperature corresponding to Y. Determine the time the solid should remain in the drier