A diffusion couple of two metals $,$ A and B$,$ was fashioned as shown: After a $700$ hour heat treatment at $1120$ degree celsius the concentration of A is $1\mathrm{.}7$ wt$\%$ at the $3\mathrm{.}5$mm position within metal B$.$ At what temperature $($in Kelvin$)$ must the diffusion couple need to be heated to produce this same concentration at $1\mathrm{.}8$mm position after $700$ hr$?$The preexponential and activation energy values for the diffusion of A and B are $3\mathrm{.}8$x$10^-5$ and $255$KJ$/$mol$,$ respectively.