A batch of wet solids is processed in a tray dryer using conditions of constant drying. The rate of drying during the constant rate period is 3.22 kg of H2O/m2h. The weight of the dry solid is 650 kg and the total area of the trays of drying is 2.3 m. The critical humidity is 12%. Calculate the time to dry a batch of this material from a moisture content (X) of 60% to 18%? ****Note: the correct answer is 38.9 hours.