Consider the following transformation involving first order...

Consider the following transformation involving first order elementary reaction in each step at constant temperature as shown below. (A+B \underset{\text{ Step 3 }}{\text{ Step } 1} C \xrightarrow{\text{ Step 2 }} P) Some details of the above reactions are listed below. ($$\begin{array}{ccc} \text{ Step } & \text{ Rate constant }\left(\mathbf{s e c}^{-\mathbf{1}}\right) & \text{ Activation energy }\left(\mathbf{k J ~ m o l}^{-\mathbf{1}}\right) \\ 1 & \mathrm{k}_1 & 300 \\ 2 & \mathrm{k}_2 & 200 \\ 3 & \mathrm{k}_3 & \mathrm{Ea}_3 \end{array}$$ If the overall rate constant of the above transformation $(k)$ is given as (k=\frac{k_1 k_2}{k_3}) and the overall activation energy (\left(\mathrm{E}_{\mathrm{a}}\right)) is (400 \mathrm{~kJ} \mathrm{~mol}^{-1}), then the value of (\mathrm{Ea}_3) is (\qquad) (\mathrm{kJ} \mathrm{mol}^{-1}) (nearest integer)