The surface tension of liquid argon is given by $\sigma=\sigma_0\left(1-T / T_c\right)^{1.28}$, where $\sigma_0=0.038 \mathrm{~N} / \mathrm{m}$ and the critical temperature $T_c=151 \mathrm{~K}$. Find the surface entropy per unit area at the triple point, $T=83 \mathrm{~K}$.