Knights and Knaves: Olivia, Bob, Judy, Dave, and Frank

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knights knaves

On an island, every inhabitant is either a knight, who always tells the truth, or a knave, who always lies. You meet Olivia, Bob, Judy, Dave, and Frank. Olivia says: "Bob is a knave." Judy says: "Frank is a knave." Dave says: "Olivia and Frank are of different types." Frank says: "If Bob is a knave, then Dave is a knight." The others say nothing. Who is a knight and who is a knave?

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Solution

Commit an attempt to unseal the proof. Write your answer — right or wrong, thinking it through is the point.

Once you've worked out who is who: how many of the 5 inhabitants are knaves? Answer with the number.

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