A sample of milk splits after 60 min. at 300 K and after 40 min. at 400 K when the population of lactobacillus acidophilus in it doubles. The activa tion energy (in kJ/ mol) for this process is closest to__________.
(Given, R = 8.3 J mol^–1 K^–1, $\ln \left( {{3 \over 2}} \right) = 0.4$, e^–3 = 4.0)