Why answer is 16?

Question

https://code.sololearn.com/caH5DSIWl1xC/?ref=app

Answer 1

func(2) returns 4.
So, func(func(2)) = func(4)

func(4) returns 16.
So, func(func(2)) = func(4) = 16.

Answer 2

Because you have a function within a function, so after the first function has run, the result of that function will be inputted.

So after the first function, the answer return is 4 (2x2).

Then 4 is inputted and 16 is the answer (4x4).