M: Everything on that shelf is worth fifty cents.
W: But if this is the signature of someone who is well-known, it might bring a lot more. I hear William Shakespeare's signature is worth about a million dollars.
M: Oh？ I can hardly read what that one says. Who wrote it？
W: The name looks like "Harold Dobson". Wasn't he a politician or something？ I' m going to buy this book and see if I can find a name looks like that in the library.
M: Good luck. Your poetry book may make you rich. But I think my seventy-five-cent mys- tery is a better buy.
Where is the conversation taking place？

A. In a second-hand book shop.
B. In a publisher' s office.
C. In a library.