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Problem 8 Explain why each of the following are tautologies. That is, what expression(s) of predicate logic did we substitute into which tautologies of propositional logic? a) (P(X) OR ((Y)) = (g(Y) OR p(x)) b) (p(X,Y) AND P(X,Y)) = P(X,Y) c) (p(X) + FALSE) = NOT P(X)