If ice homogeneously nucleates at $-40^{\circ} \mathrm{C}$ calculate the critical radius given values of $-3.1 \times 10^{8} \mathrm{J} / \mathrm{m}^{3}$ and $25 \times 10^{-3} \mathrm{J} / \mathrm{m}^{2},$ respec
tively, for the latent heat of fusion and the surface free energy.