Step-by-step explanation:
Efficiency is defined as the measure of amount of work done by a system.
Mathematically,
![Efficiency = (Energy output)/(Energy input) * 100]()
- For machine A efficiency will be as follows.
Efficiency =
![(Energy output)/(Energy input) * 100]()
=

= 25%
- For machine B efficiency will be as follows.
Efficiency =
![(Energy output)/(Energy input) * 100]()
=

= 70%
- For machine C efficiency will be as follows.
Efficiency =
![(Energy output)/(Energy input) * 100]()
=

= 75%
Thus, we can see that efficiency is maximum in machine C, therefore, machine C is the most efficient.