And this if I say when c is equal to A B, when integral over c q bar dot d r bar integral over A B A to B basically, and is d phi that gives me phi A phi B minus phi A. And what does this gives? And now that q bar dot d r bar represents, this is a measure of the fluid velocity in the direction of counter at each point. So, the velocity potential phi velocity of potential phi and here we see that this is these are the two ends points B and A, so it is the independent of the path, because it is just phi B minus phi A.