A thin sheet of iron at $800C$ is exposed to different gas atmospheres on both of its surfaces in

such a way that the composition on one of its faces is $4\%($atomic$)$ carbon and the other is $0\%$

carbon. Under steady$-$state conditions, plot the composition profile of the sample, clearly

indicating respective compositions and distances.

The thickness of the sample is $1mm$ and the changes in densities during the experiment can

be considered negligible. At $800C$ it is known that the diffusion coefficient of carbon in iron is

given by:

$D={10}^{-6}c{m}^2{s}^{-1}$ in ferrite $($Fe$-$a$)$

$D={10}^{-8}c{m}^2{s}^{-1}$ in austenite $($Fe$-$g$)$