a
Here, Input signal, \(V_{i}=2 \cos \left(15 t+\frac{\pi}{3}\right)\) and voltage gain, \(A_{v}=150\)

As \(A_{v}=\frac{V_{0}}{V_{i}}\)

\(\therefore\) Output signal, \(V_{o}=A_{v} V_{i}\)

since \(CE\) amplifier gives a phase difference of \(\pi\left(=180^{\circ}\right)\) between input and output signals,

\( \therefore \quad V_{o} =150\left[2 \cos \left(15 t+\frac{\pi}{3}+\pi\right)\right]\)

\(=300 \cos \left(15 t+\frac{4 \pi}{3}\right)\)