Power = (work done) / (time to do the work)
Work done = (force) x (distance)
Force = (weight of the crate) = (mass of the crate) x (gravity)
Crate weight = (100 kg) x (9.8 m/s²)
Force = 980 Newtons
Work done = (980 N) x (2 m) = 1,960 Joules
Power = (1,960 Joules) / (4 seconds)
Power = 490 Joules per second
(Whoever wrote the question used 10 m/s² for gravity instead of 9.8 m/s², so his answer came out to be 500 W. That's choice-B .)
Power = 490 watts
