2. A furnace wall comprises of two layers -8 cm of fire clay next to the fire box and 0.6 cm of mild steel on the outside. The inside surface of the brick is at 900 K and the steel is surrounded by air at 300 K with an outside surface coefficient of 5 W/m²K. a. estimate the heat flux through square metre of furnace wall b. estimate the outside surface temperature of steel c. what would be the percentage increase in heat flux if in addition to the conditions specified, eighteen steel bolts of 1.8 cm diameter pass through the composite wal- loper square metre of wall area? Take thermal conductivities of fire clay and steel to be 1.2 W/mK and 35 W/mK.