Active Reading Solution: Creating More Paths

You can make arbitrarily many diagrams for this process by adding more charged particle loops inside any photon line, as we did in our example.

You can also have any charged particle emit and absorb a photon.

And you can mix and match these in any way, including having one charged particle emit a photon and having a different one absorb it.

The key is that whenever lines come together there are two straight lines (representing the same kind of particle) and one wavy line, and the only lines that don't start and end inside the diagram are the initial muon/antimuon pair and the final electron/positron pair.