Provide a counter example for each that is not correct.
(a) $P \to ((Q \land R) \lor T)$, $Q \land R \to \neg P$, $S \to \neg T \models P \to \neg S$
(b) $P \to Q$, $\neg P \to R$, $Q \lor R \to S \models S$
(c) $P \to Q$, $R \to P$, $(P \land S) \lor R \models Q \to P \land R$
