Section $2$: Nitridation Process $(25$ points total$)$

$11.$ Nitridation is a process where gaseous nitrogen $(N)$ diffuses into the surface of a very long bar of PURE iron $(Fe,BCC)$ at $750C.$ What depth into the bar will reach a concentration of $0\mathrm{.}4wt\%N$ after $24$ hours if the surface concentration is set at $10$ wt$\%$ N$?**$Interpolation required for full credit.