Choose the correct option 

Here, we have,

${\mathrm{P}}_{\mathrm{A}}=\left[\mathrm{A}\right] \mathrm{RT}$

$\begin{array}{r}-{\mathrm{r}}_{\mathrm{A}}=2.5\times 400\mathrm{R}\left[\mathrm{A}\right]\text{ at }400\mathrm{K}\\ -{\mathrm{r}}_{\mathrm{A}}=2.5\times 600\mathrm{R}\left[\mathrm{A}\right]\text{ at }600\mathrm{K}\end{array}$

In $\left(\frac{6}{4}\right)=\frac{E_a}{8.314}\left[\frac{1}{400}-\frac{1}{600}\right]$

$\Rightarrow {\mathrm{E}}_{\mathrm{a}}=4135 \mathrm{J}/\mathrm{mol}$