A furnace wall consists of 125 mm wide refractory brick and 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 11000C and the room temperature is 250C. The heat transfer coefficient from the outside wall surface to the air in the room is 17 W/m2K, and the resistant to heat flow of the air gap is 0.16K/W. The thermal conductivities of refractory brick, insulating firebrick, and the plaster are 1.6, 0.3, and 0.14 W/mK respectively. Calculate:

(i) the rate of heat loss per unit area of wall surface;

(ii) the temperature at each interface throughout the wall;

(iii) the temperature at the outside surface of the wall.