A sample of milk splits after $60\mathrm{}\mathrm{m}\mathrm{i}\mathrm{n}$ . at $300\mathrm{}\mathrm{K}$ and after $40\mathrm{}\mathrm{m}\mathrm{i}\mathrm{n}$ . at $400\mathrm{}\mathrm{K}$ when the population of Iactobacillus acidophilus in it doubles. The activation energy (in $\mathrm{kJ}/\mathrm{mol}$ ) for this process is closest to ______________.
(Given, $\mathrm{R}=8.3\mathrm{}\mathrm{J}\mathrm{m}\mathrm{o}{\mathrm{l}}^{-1}{\mathrm{K}}^{-1},\mathrm{l}\mathrm{n}\left(\frac{2}{3}\right)=0.4,{\mathrm{e}}^{-3}=4.0$ )