A sample of milk splits after 60min . at 300K and after 40min . at...

$\left[ln\right]\dfrac{{k}_{2}}{{k}_{1}} = \dfrac{Ea}{R}\left[\dfrac{1}{{T}_{1}}\dfrac{1}{{T}_{2}}\right]$
$\ln \left(\dfrac{60}{40}\right) = \dfrac{Ea}{8 .3} \times \dfrac{100}{400 \times 300}$
$\ln \left(\dfrac{3}{2}\right) \times 8 .3 \times 1200 = {E}_{a}$
$⟹ {E}_{a} = 0 .4 \times 8 .3 \times 1200$
$⟹ {E}_{a} = 3984\dfrac{J}{mol} .$
$⟹ {E}_{a} = 3 .984 k\dfrac{J}{mol} .$