$1)$The self$-$diffusivity of sodium at two different temperatures is stated as follows.

DNA$($cm$^2/$s$)$

$1)4\mathrm{.}5$ x $10^-5$

$2)9\mathrm{.}2$ x $10^-5$

T$($K$)$

$1)400$

$2)667$

Derive an equation expressing the diffusivity of sodium as a function of temperature.