A layer of ice has formed on a small pond. The air just above the ice is at -5.4 °C, the water-ice interface is at 0 °C, and the water at the bottom of the pond is at 4.0 °C. If the total depth from the top of the ice to the bottom of the pond is 1.4 m, how thick is the layer of ice? The thermal conductivity of ice is 1.6 W/(m · C°) and that of water is 0.60 W/(m · C°).