Sequential Kinetics

I was solving some problems on chemical kinetics, then I was just struck at some ques of sequential reaction kinetics.

Given reactions $$\ce{O_3 + Cl \rightarrow O_2 + ClO ~~~ k_1=5.2 \times 10^9~Lmol^{-1}s^{-1}}$$

and $$\ce{ClO + O \rightarrow O_2 + Cl ~~~ ~~~ k_2=2.6 \times 10^{10} ~Lmol^{-1}s^{-1}}$$

So, which value is closest to rate const of overall net reaction? $$\ce{O_3 + O \rightarrow 2O_2}$$

and the answer given was $=5.2 \times 10^9 ~\mathrm{Lmol^{-1}s^{-1}}$

Therefore I am confused, how did they find the rate const of the net reaction?

The RDS is the one with the lowest rate constant. Hence in this case the overall rate of the reaction is $5.2 \times 10^9 Lmol^{-1}s^{-1}$