DN_S27_Q019. Mr and Mrs Jones inviting four couples

Mr. and Mrs. Jones invite four other couples over for a party. As people arrive, various handshakes take place. As one would expect, none of the spouses shake hands with each other, and no one shakes hands with the same person twice. At the end of the night, Mr. Jones polls the other nine people about the number of hands they shook, and gets a different answer from each of them. How many people did Mrs. Jones shake hands with?