Where are they most possibly?

M: Good morning, Madam. What can I do for you?
W: Good morning. How much should I pay for these books to be sent to New York?
M: Hm, 20 dollars. Anything else?
W: Yes, a two-dollar stamp, please.
M: That will be 22 dollars all together.
W: Here’s 25.
M: Thank you. And here’s the change.
W: Thank you.
M: You’re welcome.