A composite wall is formed by sandwiching a 0.1 m thickness material between two steel slabs. The thermal conductivity of steel is 20 W/mK . We need to calculate the thermal conductivity of the material. The thickness of each steel slab is 0.4 m. The heat flux given at steady state is 20KW/m^2. The inner temperature of this composite wall is 700 K and the outer temperature is 200 K. Also calculate the temperature at the interface.