a
\({V_{\text {gain }}=\left(\frac{\Delta  I_{C}}{\Delta I_{B}}\right) \frac{R_{\text {out }}}{R_{\text {in }}}=\left(\frac{5 \times 10^{-3}}{100 \times 10^{-6}}\right) \times 10^{3}}\)

\(=\frac{1}{20}  \times 10^{8}=5 \times 10^{4} \)

\(P_{\text {gain }} =\left(\frac{\Delta I_{C}}{\Delta I_{b}}\right)\left(V_{\text {gain }}\right) \)

\(=\left(\frac{5 \times 10^{-3}}{100 \times 10^{-6}}\right)\left(5 \times 10^{4}\right)\)

\(=2.5 \times 10^{6}\)