Answer:
η = 0.882 = 88.2 %
Explanation:
The efficiency of the pulley system can be given as follows:

where,
η = efficiency of pulley system = ?
W_out = Output Work = (600 N)(0.6 m) = 360 J
W_in = Input Work = (35.7 N)(11.43 m) = 408.051 J
Therefore,

<u>η = 0.882 = 88.2 %</u>
Let the observer be 'd' distance away from the thunderstorm and let light take 't' time to reach the observer
Since the speed of sound and light remains constant in a particular medium, we can use
Speed = Distance/Time
For light,
3 x 10^8 = d/t
t = d/(3 x 10^8) -1
For sound,
339 = d/(t + 30) -2
Putting value from 1 in 2.
d = 10^4 m(approx)
It's either staying there or is going at the same pace