A 75 mm thick wooden plate contains 2.8 % by mass water, relative to dry wood, which corresponds to a mass fraction of ξAα = XXXXXXXXXXAt equilibrium with the environment the mass fraction is reduced...

A 75 mm thick wooden plate contains 2.8 % by mass water, relative to dry wood, which corresponds to a mass fraction of ξAα = 0.218. At equilibrium with the environment the mass fraction is reduced to ξAS = 0.065. How long does it take for the mass fraction of water in the middle of the plate to fall to ξA(x = 0) = 0.08? The diffusion coefficient of water in wood is D = 1.2 · 10−9 m²/s.