The gas phase decomposition of n$2$o$5$ has the overall reaction stoichiometry $2$N$2$O$5$ gives $4$no$2$ plus O$2.$

The first $2$ steps in the mechanism are

$2$N$2$O$5$ gives $2$ NO$2$ plus $2$ NO$3$

The second step given NO$2+$ NO$3$ gives NO$2+$ NO$+$O$2,$ what is the third and the final step in the mechanism, don ot include physical states in your answER