Given:
density of air at inlet, 
density of air at inlet, 
Solution:
Now,
(1)
where
A = Area of cross section
= velocity of air at inlet
= velocity of air at outlet
Now, using eqn (1), we get:
= 1.14
% increase in velocity = 
=114%
which is 14% more
Therefore % increase in velocity is 14%
Work done is given by product of force and displacement due to that force
So here we will have
here we know that
Now work done is given as
so it will do 16 J work to move the box
High frequency , it is because wavelength is inversely proportional to frequency
The correct answer is C) Rainfall
