I am having trouble on setting this problem up.

You are in a room with two waiters and two glasses: a blue glass and a green glass. One glasshas water and the other glass has poison. One waiter always tells the truth and the other waiteralways tells lies. You ask one of the waiters, “If I asked the other waiter to identify the glasswith poison, what would she say?” The waiter says, “The other waiter would say the green glasshas poison.” Which glass has poison? Prove your answer is correct