Prior to treating pine logs to prevent them from warping, the logs are kiln dried to remove the moisture. The moisture content of the solid surface is in equilibrium with the air and can be assumed to be constant at 5%. The initial moisture content is 30% and the maximum permissible concentration is 15%. If the logs are 12.2 m long with a diameter of 0.3 m, determine the time necessary for them to dry. The effective diffusivity of water in pine may be assumed to be constant with a value of 1.0×10-7 m2/s.