A two-transistor series voltage feedback amplifier is shown in Figure P2.24(a). This AC equivalent circuit neglects the bias resistors and the shunt capacitors. A block diagram representing the circuit is shown in Figure P2.24(b). This block diagram neglects the effect of $h_{r e}$, which is usually an accurate approximation, and assumes that $R_2+R_L \gg R_1$. (a) Determine the voltage gain $v_{\mathrm{o}} / v_{\mathrm{in}}$. (b) Determine the current gain $i_{c 2} / i_{b 1}$. (c) Determine the input impedance $v_{\text {in }} / i_{b 1}$.