How many people will be at the party?

W: Jack, would you like to come to my house with your wife for dinner at six tomorrow evening?
M: We would like to. Who else will be there?
W: Well, I also invite the White’s.
M: That sounds great. I enjoy making friends, chatting with others. I always stay at home and feel bored. By the way, is it a formal dinner or informal one?
W: Informal, of course, just feel at home.
M: Great! Oh, I can’t wait.