what's the different between "I bought a book for him." and "I bought a book to him." ? Are they both right?Then if i say"I bought a book for Tom." Who will really pay for the book? Does it mean "I bought Tom a book as a present" or "I help Tom to buy a book, and when I give the book to him he will pay me back ." How can I separate these two situations? Thank you for all your answers!