The walls are constructed from an inner fire brick wall 25 thick of thermal conductivity of 0.4/, a layer of ceramic blanket insulation of thermal conductivity 0.2 / and 8 thick, and a steel protective layer of thermal conductivity of 55 / and 2 thick. The inside temperature of the fire brick layer was measured at 600 and the temperature of the outside of the insulation 60. 4.1.Calculate the rate of the heat