An industrial furnace is made of fireclay brick of thickness L = 0.25 m and thermal conductivity k = 1.0 W/(m +C). The outside surface is to be insulated with material of thermal conductivity k = 0.05 W/(m. C). Determine the thickness of the insulation layer in order to limit the heat loss from the furnace wall to q = 1000 W/m when the inside surface of the wall is at 1030C and the outside surface at 30C.