Nitrogen from a gaseous phase is to be diffused into pure iron at $700C.$ If the surface concentration is maintained at $0\mathrm{.}20$ wt $\%N,$ what will be the concentration $($in weight percent$)2\mathrm{.}4mm$ from the surface after $8\mathrm{.}1h?$ The diffusion coefficient for nitrogen in iron at $700C$ is $1\mathrm{.}3{10}^{-10}\frac{m^2}{s}.$

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