For the overall reaction 2 NO(g) + O₂(g) → 2 NO₂(g), one proposed first elementary step is
Step 1 (slow): NO(g) + O₂(g) → NO₃(g)
Write a single elementary Step 2 that, together with Step 1, produces the overall reaction. The step you provide must involve only bimolecular collision of gas-phase species.