When a transistor amplifier having current gain of 75 is given an input signal voltage $V_{\mathrm{i}}=2 \sin \left(157\mathrm{t}+\frac{\mathrm{\pi }}{2}\right)mV$ .If input  resistance is ${\mathrm{R}}_{\mathrm{i}}=500\mathrm{\Omega }$ and resistance in the collector circuit is  $2000\mathrm{\Omega }$, The output signal voltage is

Since the current gain is $\mathrm{\beta }$ = 75 , Voltage gain ${\mathrm{A}}_{\mathrm{v}}=\frac{2000}{500} \mathrm{x} 75=300$

$\therefore$The transistor must be a common emitter amplifier. 

Peak value of output voltage = $300 \mathrm{x} 2 \mathrm{x} {10}^{-3}\mathrm{v}=0.6V$

In common emitter configuration, The phase difference between output and input signal voltage is ${180}^{\mathrm{o}}$

$\therefore V_0=600 \sin (157\mathrm{t}+\frac{\mathrm{\pi }}{2}+\mathrm{\pi }) mV$