Using the Interdiffusion $($Vacancy$)$ table below, answer the following:

$($a$)$ Calculate the diffusion coefficient for Zn in Cu at $520C.$

${10}^{Ex\text{:}30}\frac{m^2}{s}$

$($b$)$ What time $($in h $)$ will be required at $630C$ to produce the same diffusion result $($in terms of

concentration at a specific point$)$ as for $11$ h at $520C?$

Ex: $0\mathrm{.}789$ h