Nitrogen from a gaseous phase is to be diffused into pure iron at $700C.$ If the surface concentration is maintalined at $0\mathrm{.}19$ wt: $N,$ what will be the concentration $($in weight percent$)1\mathrm{.}9mm$ from the surface after $5\mathrm{.}1h?$ The diffusion coefficient for nitrogen in iron at $700C$ is $1\mathrm{.}2{10}^{-10}\frac{m^2}{s}.$

$\backslash$table$[[z,$enf$(z),z,$erf$(z),z,$erf$(z)$