Correct option is C
Input power = 400 W
Mass of water lifted = 500 kg
Height lifted = 30 m
Time taken = 10 minutes = 600 seconds
Acceleration due to gravity = 10 m/s²
The useful power (output power) is the work done per second, i.e., the power required to lift the water.
Work done = Potential Energy
= mgh
= 500 × 10 × 30
= 150,000 Joules
Since Power = Work/Time,
Output Power = 150,000/600
= 250 W
η = 250/400 × 100 = 62.5%
