2) The walls of a cold storage room are composed of two layers, inner layer a and outer layer b. Layer a has a thickness of 15 mm with a thermal conductivity of 0.16 W/m K, while layer b has a thickness of 120 mm with a thermal conductivity of 0.03 W/m K. The temperature inside and outside of the cold storage room is kept constant at 250 K and 300 K, respectively. a. Calculate the heat transfer rate per unit area. (10 points) b. Calculate the temperature between the two layers. (10 points)