Heat and Mass Transfer in Food Processing

A solid food product has thermal conductivity $k = 0.48\text{ W/(m}\cdot\text{K)}$, density $\rho = 1200\text{ kg/m}^3$, and specific heat $c_p = 4000\text{ J/(kg}\cdot\text{K)}$. The volumetric heat capacity is $\rho c_p = 1200 \times 4000 = 4.8 \times 10^6\text{ J/(m}^3\cdot\text{K)}$. The thermal diffusivity $\alpha = k / (\rho c_p)$ in m$^2$/s is $1.0 \times 10^{-m}$. The value of $m$ is: