In a coal-fired power plant, a furnace wall consists of a 125-mm-wide refractory brick and a 125-mm-wide insulating firebrick separated by an air gap. The outside wall is

covered with a 12 mm thickness of plaster. The inner surface of the wall is at 1100◦C,

and the room temperature is 25◦C. The heat-transfer coefficient from the outside wall surface to the air in the room is 17 W/m2 K, and the resistance to heat flow of the airgap is 0.16 K/W. The thermal conductivities of the refractor brick, the insulating firebrick, and the plaster are 1.6, 0.3, and 0.14 W/m K, respectively. Calculate the rate of heat loss per unit area of wall surface​