A steam turbine is used to turn a generator. The power entering the turbine is $P_I$, and the power leaving it is $P_O$. The power lost in the turbine is $P_L$, as shown. 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$\frac{P_O}{P_I}$