How long may I keep/borrow it?

[diamondcutter]

Liu Ying: Good afternoon.
Librarian: Good afternoon. Can I help you?
Liu Ying: Do you have From Earth to Moon?
Librarian: Let me see ... Ah, here it is.
Liu Ying: Thank you. How long may I keep it?
Librarian: Two weeks.

Source: English Book 3, for junior middle school students, People’s Education Press, 1982.

I think the verb “keep” in “How long may I keep it?” can be replaced with “borrow”. Could you tell me which word you use more often in this context?

 

[Jemima23]

Not a teacher.

It can be replaced, but you have to use the preposition "for", as in: "How long can I borrow this book for?" I'd personally prefer this one, but I think both of them are acceptable.

 

[diamondcutter]

Thanks, Jemima23.

For this sentence: "How long may I keep it", it's not necessary to use the preposition "for". Am I right?

 

[Rover_KE]

You're right.

 

[diamondcutter]

Thanks, Rover_KE.

1. How long may I keep this book?
2. How long may I borrow this book for?

These two sentences have the same meaning in the context in #1. Sentence 2 needs the preposition “for” while Sentence 1 doesn’t. Would you please tell me why?