A carpenter has obtained a wood board, but needs to dry it out first. The board is 75 mm thick and the internal moisture content is 60% by weight. The carpenter is drying the two long sides simultaneously, and the equilibrium moisture content at those surfaces due to the drying is 10% by weight. The diffusivity is 3.72 * 10-6 m 2 /h. Calculate the time it will take for the center to reach the following moisture levels: a) 30%
b) 10%
c) 2%
Additionally, based on your answers to a-c, is the board usable? In other words, would the carpenter be able to make something out of it and sell the finished product, or would the board take too long to dry?