$6$ The diffusion coefficients for silver in copper are given at two temperatures:

$T(C),D(\frac{m^2}{s})$

$650,5\mathrm{.}5{10}^{-16}$

$900,1\mathrm{.}3{10}^{-13}$

$($a$)$ Determine the values of $D_0$ and $Q_d.$

$($b$)$ What is the magnitude of $D$ at $875C?$

$7.($a$)$ Calculate the diffusion coefficient for copper in aluminum at $=136,000\frac{J}{m}ol,D_0=6\mathrm{.}5**{10}^{-5}\frac{m^2}{s})$

$($b$)$ What time will be required at $600C$ to produce the same diffusion result $($in terms of concentration at a specific point$)$ as for $10h$ at $500C?$

$2$