Knights and Knaves: Grace, Frank, Niaj, and Heidi

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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 Grace, Frank, Niaj, and Heidi. Grace says: "Niaj is a knight." Frank says: "Niaj is a knave." Niaj says: "Frank is a knave or Heidi is a knave." Heidi says: "Grace is a knight and Frank is a knave." 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 4 inhabitants are knaves? Answer with the number.

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