A $3 \mathrm{~cm}$-square plate has its edge temperatures maintained at $30^{\circ} \mathrm{C}, 20^{\circ} \mathrm{C}, 10^{\circ} \mathrm{C}$, and $0^{\circ} \mathrm{C}$, as shown. The faces of the plate are well insulated. Use Gauss-Seidel iteration on a I cm-square mesh to obtain the steady-state temperature distribution. Give the interior node temperatures after the first four iterations.