8. (20) Predicates P and Q are defined below. The domain of discourse is the set of all positive integers. P(x):x is prime Q(x): x is a perfect square, i.e. x-y2 for some integer y Indicate whether each logical expression is a proposition. If it is a p roposition. give its truth value. a) t20x) b) Vx Q(x) ^ P'(x) c) VxQ(x) v P(3) d) 3x (Q(x) P(x)) e) Vx(Q'(x) v P(x)