[Problem 2] The roof of a house is 6 m long, 8 m wide, and 0.25 m thick. It is made of a flat layer of concrete whose thermal conductivity is k = 0.8 W/m-K. The temperatures of the inner and the outer surfaces of the roof are measured to be 15°C and 4°C, respectively. Calculated heat loss through the roof in [W]. Concrete roof 0.25 m 8 m 6 m 4°C 15°C