The reaction of ${\mathrm{NO}}_2\left(g\right)$and ${\mathrm{O}}_3\left(g\right)$ is first-order in ${\mathrm{NO}}_2\left(g\right)$ and ${\mathrm{O}}_3\left(g\right)$

$2{\mathrm{NO}}_2\left(g\right)+{\mathrm{O}}_3\left(g\right)⟶{\mathrm{N}}_2{\mathrm{O}}_5\left(g\right)+{\mathrm{O}}_2\left(g\right)$

The reaction can take place by mechanism :

P) ${\mathrm{NO}}_2+{\mathrm{O}}_3\stackrel{\text{ slow }}{⟶}{\mathrm{NO}}_3+{\mathrm{O}}_2$

${\mathrm{NO}}_3+{\mathrm{NO}}_2\stackrel{\text{ fast }}{⟶}{\mathrm{N}}_2{\mathrm{O}}_5$

Q) ${\mathrm{O}}_3\underset{k_{\mathrm{b}}}{\stackrel{k_{\mathrm{o}}\text{ fust }}{\rightleftharpoons }}{\mathrm{O}}_2+\left[\mathrm{O}\right]$

${\mathrm{NO}}_2+\mathrm{O}\stackrel{\text{ slow }}{⟶}{\mathrm{NO}}_3$

${\mathrm{NO}}_3+{\mathrm{NO}}_2\stackrel{\text{ fast }}{⟶}{\mathrm{N}}_2{\mathrm{O}}_5$

Select the correct mechanism.