Solution:Option C) is the correct answer because,
Diameter of well = 20m
radius of well(r)= Diameter ÷ 2=10m
Height of well (h) = 14m
Width of embankment = 5m
The earth taken out is spread all around the well, therefore, the radius of embankment if taken from the centre will be R.
R=Radius of wheel+widthR
= r + 5R
Now, to find the height of the embankment we have to equate the volume of the well and the volume of the embankment.
Volume of well = Volume of embankment
∴ The height of the embankment = 11.2m.