Option C:
The coefficient of
is 40.
Solution:
Given expression:

Using binomial theorem:

Here 
Substitute in the binomial formula, we get

Now to expand the summation, substitute i = 0, 1, 2, 3, 4 and 5.


Let us solve the term one by one.






Substitute these into the above expansion.

The coefficient of
is 40.
Option C is the correct answer.