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.