A wet clay brick measuring 2 * 4 * 6 inches has an initial water content uniform 12% by weight. At time t = 0, the brick is exposed on all sides to air so that the moisture content of the surface is kept at 2% by weight. After 5 h, the average moisture content is 8% by weight. Estimation: (a) the diffusivity of the water in the clay in cm2 / s; and (b) the additional time for the average moisture content to reach 4%. in weight. All moisture content is on a dry basis