How old is the woman going to be?

M: It’ s your fiftieth birthday. You decide.
W: I’ d like you to organize a surprise party for me.
M: Sylvia, I know what you want. But a surprise party is impossible. Don’t you remember when I tried to organize a surprise party for your fortieth? You found out right away.
W: Don’t remind me. I was so disappointed.
M: I remembered to get everything ready. But I just forgot to tell people that it was supposed to be a surprise. But the party wasn’ t disappointing. I mean, it wasn’ t a surprise, but it was great.
W: Well, I really don’t care what you do. Do whatever you want.
M: Oh, come on, Sylvia. Let’ s plan something interesting. We could have a swimming party, or a covered-dish supper. It could be fun.
W: Let’ s just go out to dinner with a few friends.
M: But why?
W: Because it’ s easy. I don’t want to have to do all the planning.