= Solution
The first four-fermion operator is the low-energy <Fermi interaction> obtained by replacing the crossed $W$ propagator in the charged-current diagram by $-g_{\mu\nu}/M_W^2$. The second operator is obtained analogously from the $Z$-exchange <weak neutral current>; $c_V$ and $c_A$ are its electron vector and axial-vector couplings. Thus the two terms represent respectively the charged-current and neutral-current diagrams in part (v), with their interference retained when the amplitude is squared.
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