A sheet of steel 1.5 mm thick has nitrogen (N2) atmospheres on both sides at 1200°C and is permitted to achieve steady-state diffusion condition. The diffusion coefficient for N2 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 N2 in the steel at the high-pressure surface is 4 kg/m3 . How far into the sheet from the high-pressure side will the concentration be 2.0 kg/m3 ? Assume a linear concentration profile.