A wind turbine produces $54\ \text{kW}$ of useful power from an input of $180\ \text{kW}$ of wind power. Which calculation shows the percentage efficiency of the turbine?
- A$\frac{54000}{180000} \times 100\ \%$
- B$\frac{180000}{54000} \times 100\ \%$
- C$\frac{54000 \times 100}{180000}\ \%$
- D$\frac{180000 \times 100}{54000}\ \%$