A dryer with air circulation parallel to the drying surface is used to dry 400 kg of granular solid material with an initial humidity of 0.38 kg of H2O/kg of dry solid. Critical humidity is reached with 0.195 kg of H2O/kg of dry solid. The dimensions of the drying area are 5 x 5 m. Heat transfer is by convection from an air stream flowing parallel to the surface of the solid at a velocity of 7.2 m/s. The drying air is at a temperature of 65oC and a humidity of 0.010 kg H2O/kg of dry air. The wet bulb temperature of the air is 29oC, the latent heat at this temperature is 2433 kJ/kg, and the humidity at the wet bulb temperature is 0.026 kg H2O/kg dry air. a) Estimate the drying rate for the constant rate period e; b) The constant rate period.