d
Average Power \(=\frac{\text { total } \text { work done }}{\text { total time }}\)

So,\(P=\frac{m g h}{t}\)

\(\frac{P_1}{P_2}=\frac{\frac{m_1 g h}{t_1}}{\frac{m_2 g h}{t_2}}=\frac{m_1}{t_1} \frac{t_2}{m_2}\)

\(\frac{P_1}{P_2}=\frac{300 \times 2}{5 \times 50}=\frac{12}{5}=\frac{3 \sqrt{x}}{\sqrt{x}+1}\)

\(12 \sqrt{x}+12=15 \sqrt{x}\)

\(3 \sqrt{x}=12\)

\(x=16\)