A 0.27-m-thick sheet of ice covers a lake. The air temperature at the ice surface is -10°C. In five minutes, the ice thickens by a small amount. Assume that no heat flows from the ground below into the water and that the added ice is very thin compared to 0.27 m. Find the number of millimeters by which the ice thickens. (Assume a thermal conductivity for ice of 2 J/(s·m·C°) and a latent heat of fusion of 3.35x105 J/kg.)