a
\(R_{0}=500\, \mathrm{k\Omega} ; \alpha=0.98\)

Power gain \(=6.0625 \times 10^{6}\)

we have, voltage gain \(\mathrm{A}_{\mathrm{V}}=\beta \cdot \frac{\mathrm{R}_{0}}{\mathrm{R}_{\mathrm{i}}}\)

But current gain,

\(\beta=\frac{\alpha}{1-\alpha}=\frac{0.98}{1-0.98}=49\)

\(\therefore A_{V}=49 \times \frac{500 \times 10^{3}}{R_{i}}=\frac{24.5 \times 10^{6}}{R_{i}}\)

Given \(6.0625 \times 10^{6}=\mathrm{A}_{\mathrm{V}} \times \beta\)

\(=\left(\frac{24.5 \times 10^{6}}{\mathrm{R}_{\mathrm{i}}}\right) \times 49\)

or \(\quad \mathrm{R}_{\mathrm{i}}=\frac{24.5 \times 49}{6.0625}=198 \,\Omega\)