There are four friends, Andrea, Barbara, Clara, and Diana, all of whom share the same birthday. They've decided to trade gifts with one another such that no girl receives her own purchase and no girl knows the identity of the buyer of the gift she receives.
Then the 4 gifts turn out to be a book, a coupon, a dress, and a mug, and the following information is additionally revealed to all of them:
Andrea bought a dress but didn't receive a mug.
Barbara received a mug but didn't buy a coupon.
Diana then truthfully claims that she knows the item that everyone bought, but she can't exactly match each item to its receiver.
What item did Clara receive?