The reaction of formation of phosgene from CO and $\text{Cl}_2$ is $\text{CO} + \text{Cl}_2 \rightarrow \text{COCl}_2$. The proposed mechanism is:

(i) $\text{Cl}_2 \rightleftharpoons 2\text{Cl}$ (fast)

(ii) $\text{Cl} + \text{CO} \rightleftharpoons \text{COCl}$ (fast)

(iii) $\text{COCl} + \text{Cl}_2 \xrightarrow{k_5} \text{COCl}_2 + \text{Cl}$ (slow)

Find the correct expression of rate law: