Evaporation and Drying

Grain drying follows Lewis' thin-layer equation $\frac{M - M_e}{M_0 - M_e} = e^{-k t}$. A grain lot with initial moisture content $M_0 = 24\%$ (d.b.) is dried to $M = 16\%$ (d.b.) in $2.0\text{ hours}$. The equilibrium moisture content $M_e = 12\%$ (d.b.). The thin-layer drying constant $k$ in $\text{h}^{-1}$ is ________ (round off to 3 decimal places).