# Determining Feynman rules from Lagrangian

To preface, I'm not a physics major so I've never taken a QFT class before. But I'm working on something that requires me to find the amplitude of that following Lagrangian:

$$\mathcal{L} = -\frac{1}{4} F_{\mu\nu}F^{\mu\nu} +\bar\psi(i\partial_s -eA_s - m)\psi + \frac{1}{2} \partial_\mu \phi \partial^\mu \phi - \frac{1}{2} m_\phi \phi^2 - \frac{i\lambda}{\sqrt{2}}\phi\bar\psi\gamma^5 \psi$$ where $\partial_s$ and $A_s$ is the Feynman slash notation, $\psi$ is a fermion of charge $e$ and mass $m$, $\phi$ is a psuedoscalar, and the last term is a Yukawa potential.

From what I've read online, it seems that to find the amplitude, I need to first determine the Feynman rules from this Lagrangian. Then use those rules to determine the amplitude.

Since this is a QED Lagrangian + a Yukawa potential, can I find the Feynman rules for the QED Lagrangian and the rules for the Yukawa potential separately and then somehow combine them? If not, how should I begin to determine the Feynman rules for this Lagrangian?

$$\frac{i}{p^2-m_\phi^2}.$$
As for the interaction term, this corresponds to a vertex involving a $\bar\psi$, $\psi$ and $\phi$, i.e. an electron, anti electron and scalar particle, to which we associate the factor,
$$\frac{\lambda}{\sqrt 2} \gamma^5.$$
In terms of mass dimension, $[\phi] = [\psi] = [\bar\psi] = 1$, and so the Yukawa interaction requires a coupling constant with $[\lambda] = 1$ which corresponds to a super renormalizable interaction, though the theory as a whole is renormalizable.