A propositional formula is called a tautology if it evaluates to 1 for all possible values of its variables, a contradiction if it always evaluates to 0, and a contingency otherwise. Classify each expression below as tautology/contradiction/contingency (enter the full word as your answer). For those that are tautologies or contradictions, can you see why this is the case without using a truth table or simplifying the expression? Expression Q (R (P= ( PR))) tautology/contradiction/contingency tautology ( PQ)^((P) = 0) (PAQ) P ( PQ) VP (QVP) AP