A sheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200°C and is permitted to achieve a steady-state diffusion condition. The diffusion coefficient for nitrogen in steel at this temperature is 6 × 10^-11 m²/s, and the diffusion flux is found to be 1.2 × 10^-7 kg/m²-s. Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m³. How far into the sheet from this high-pressure side will the concentration be 2.0 kg/m³? Assume a linear concentration profile.