2. The inner and outer surfaces of a 0.5m thick and 5m x 9m north wall of an electrically heated home are maintained at temperatures of 50C and 20C, respectively. The rate of heat transfer through this wall is 2500W. (a) Determine the thermal conductivity of that wall if the temperatures of the surfaces are maintained constant for a period of 6h. (b) determine the total heat loss through the wall for that period, and (c) the cost of that heat loss if the cost of electricity is 0.09$/kWh. (40