A thin metal sheet is exposed to nitrogen gas at 1150 C. The nitrogen concentration is higher on one side of the sheet than the other and maintained at constant levels on each side. the diffusion coefficient for nitrogen in the metal at 1150 C is 1x10^-11 m^2/s and the end is 3.5 kg/m^3, what is the nitrogen concentration at a position 2mm into the sheet away from higher concentration end?