$(5$ points$)$ If the activation energy for diffusion is $1\mathrm{.}3$ eV $,$ how long will it take for

the carbon to reach the same $wt\%($i$.$e$.,1wt\%)$ at the same depth $($i$.$e$.,4\mathrm{.}0$ mm $),$ if

the temperature is raised to $1227C.$

a$.10\mathrm{.}5$ hours

b$.21\mathrm{.}0$ hours

c$.46\mathrm{.}2$ hours

d$.55\mathrm{.}0$ hours