A、Ten yuan and ninety fen. B、Twenty yuan and ninety fen. C、Twenty-one yuan and fifty fen. D、Ten yuan and fifty fen. C

M: Will you please show me that notebook?
W: Certainly.
M: How much is it?
W: Twanty-one yuan and fifty fen.
M: Hm. It’s certainly nice, but it’s a bit more than I was thinking of paying. I don’t think I’ll take it.
W: How about that size? It’s also very good and much cheaper.
M: Let me see one.
W: This size is ten yuan and ninety fen.
M: That’s very reasonable. I’ll take it then.
6. How much does the first notebook cost?