A sheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at \(1200^{\circ} \)C and is permitted to achieve a steady-state diffusion condition. The diffusion coefficient for nitrogen is steel at this temperature is \(6x10^{-11} m^2/s\), and the diffusion flux is found to be \(1.2x10^{-7} {kg \over m^2 s}\). Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 \(kg \over m^3\). How far into the sheet from this high-pressure side will the concentration be 2.0 \(kg \over m^3\)? Assume a linear concentration profile.