A plane wall built from fire-bricks is 200 mm thick. The temperature at the inner and outer surfaces of the wall is 1000°C and 200°C respectively. The thermal conductivity of the wall material varies linearly with temperature as k = k0 (1+bt), where ko is 0.7 kcal / m-h°C and b is 0.0005/°C. Determine the temperatures at points 50 100 and 150 mm away from the higher temperature surface. What would be the error in the temperatures calculated on the basis of an average thermal conductivity? Also determine the heat flux through the wall.