Which reaction to consider for overall rate

So I have a multistep reaction


\begin{align}
\ce{4 NH3 + 5 O2 &-> 4 NO + 6 H2O}\\
\ce{2 NO + O2 &-> 2 NO2}\\
\ce{3 NO2 + H2O &-> 2 HNO3 + NO}
\end{align}


If I know the initial decreasing rate of $\ce{O2}$ and want to find the initial overall reaction rate, can I just look at the coefficient in the rate-determining step or do I need to consider $\ce{O2}$ in the other step too?


Also if I want average rate over a period of time, is it still the same?


