A steam turbine is used to turn a generator. The turbine has input power $P_I$ and output power $P_O$. The power lost in the turbine is $P_L$, as shown below. What is the efficiency of the turbine?
- A$\frac{P_L}{P_O}$
- B$\frac{P_I}{P_O}$
- C$\frac{P_L}{P_I}$
- D$\frac{P_O}{P_I}$