Problem 1.3. (a) Verify by truth table that ( P Q ) V(QP) (1.2) is valid (b) A propositional statement is satisfiable if and only if there is an assignment of truth values to its variables which make the statement true. Explain why PE-P (1.3) is not satisfiable. (c) A set of propositional formulas P, ..., Pk is consistent if and only if there is an environment in which they are all true. Write a formula, S, so that the set P1, ..., Pk is not consistent if and only if S is valid