A piece of $Cu-10\%Zn$ alloy is wanted to be zincified in an atmosphere of evaporated $Zn$

at $800C$ at which the surface concentration can be hold at $35\%Zn.$

$log{D}^{C{u}_{zn}}=log(0\mathrm{.}033)-38,\frac{000}{2\mathrm{.}3}RT$

a$)$ What will be the $Zn$ concentration at a depth of $0\mathrm{.}1mm$ and $17hrs$ exposure time.

b$)$ Design a process which will give you a $25\%$ Zn containing alloy at the same depth.