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.