Which formula shows the efficiency of a system?
- A$\dfrac{\text{total energy input}}{\text{useful energy output}}$
- B$\dfrac{\text{useful energy output} + \text{wasted energy output}}{\text{total energy input}}$
- C$\dfrac{\text{useful energy output}}{\text{total energy input}}$
- D$\dfrac{\text{wasted energy output}}{\text{total energy input}}$