You are at 20.1711° N, 85.6861° E

What is it?
You see an old abandoned mansion.
But, your faith in Einstein is strong.
You enter the mansion. And then-

You find Dr. Scientist's pen.

This is it.
The doctor must be somewhere around.
You begin to search the place. And then,

You see a blood stained note.
You recognize the handwriting.

THE NOTE:

There is a town west of India-Pakistan
border where an Indian rupee is worth 90
paisa in Pakistani currency. In the town just
east of the border, Pakistani rupee is
worth 90 paisa in Indian currency.
Bajrangi bhaijan went into the Pakistan
town and bought a 10 paisa soda. He paid
for it with a Pakistani rupee and he was
given an Indian rupee in change since the
Indian rupee is worth only 90 paisa there.
Crossing the border into India he
bought a 10 paisa soda in the Indian town,
paid for it with the Indian rupee he just got
in Pakistan and received a Pakistani rupee
in change since the Pakistani rupee is worth
only 90 paisa east of the border.
He goes back to the Pakistan and buys
another soda then back to the India and
buys another and does this day and night.
Who pays for the soda?

E-mail the answer to devashish.sonowal@niser.ac.in

Give proper justifications.