Answer:
(a) 86.65 J
(b) 149.65 J
Solution:
As per the question:
Diameter of the pool, d = 12 m
⇒ Radius of the pool, r = 6 m
Height of the pool, H = 3 m
Depth of the pool, D = 2.5 m
Density of water, 
Acceleration due to gravity, g = 
Now,
(a) Work done in pumping all the water:
Average height of the pool, h = 
h = 
Volume of water in the pool, V = 
Mass of water, 

Work done is given by the potential energy of the water as:

(b) Work done to pump all the water through an outlet of 2 m:
Now,
Height, h = 2.75 + 2 = 4.75
Work done,