A very large industrial annealing furnace has a double wall constructed of 30cm of solid brickwork in contact with an outer cladding of 0.5cm of steel. Assume that the furnace has a total wall and roof surface area of 36m2 and ignore any heat loss into the floor. The inside of the furnace is maintained at a constant year round temperature of 800o C, and you can assume the air outside the furnace is at a constant 20o C. The convection coefficient for all solid-air surfaces can be assumed to be 20 Wm-2 K-1 , the thermal conductivity of brick is 0.6 Wm-1 K-1 , and the thermal conductivity of the steel is 40 Wm-1 K-1 . Calculate the energy loss per year through the walls and roof, and hence calculate the annual furnace energy costs if electricity costs 20p per kW.hour ("kilowatt hour").