The mechanical efficiency ( _ m ) of an I.C. engine is equal to (where I.P. = Indicated power, B.P. = Brake power and F.P. = Frictional power)

Answer: Option B

The mechanical efficiency $$\left({\eta }_{\text{m}}\right)$$ of an I.C. engine is equal to $$\frac{\text{B}\text{.P}\text{.}}{\text{I}\text{.P}\text{.}}$$
Where
I.P. = Indicated power
B.P. = Brake power
F.P. = Frictional power