= Solution
The <quantum electrodynamics> interaction is $\mathcal L_{\rm int}=-e j^\mu A_\mu$, where the <Dirac electromagnetic current> is $j^\mu=\bar\psi\gamma^\mu\psi$. Under <parity symmetry in quantum field theory>,
$$
j^\mu(x)\mapsto {\Lambda_P^\mu}_\nu j^\nu(x_P),
\qquad \Lambda_P=\operatorname{diag}(1,-1,-1,-1).
$$
Invariance of the interaction therefore requires the <electromagnetic four-potential> to transform as the same <Lorentz four-vector>:
$$
\boxed{\widehat P A^\mu(x)\widehat P^{-1}={\Lambda_P^\mu}_\nu A^\nu(x_P)},
$$
so $A^0$ is parity even and $\mathbf A$ is parity odd. Under <charge conjugation>, the current is odd, $j^\mu\mapsto-j^\mu$, so invariance requires
$$
\boxed{\widehat C A^\mu(x)\widehat C^{-1}=-A^\mu(x)}.
$$
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