Answer:
[tex]n=\frac{P_{out}}{P_{in}}[/tex]
Step-by-step explanation:
We know that,
[tex]\text{Energy efficiency}=\frac{\text{Energy out put}}{\text{Energy in put}}[/tex]
If [tex]P_{in}[/tex] represents the energy input,
[tex]P_{out}[/tex] represents the energy output,
And, n represents energy efficiency,
Hence, the required formula would be,
[tex]n=\frac{P_{out}}{P_{in}}[/tex]
i.e. OPTION B is correct.