Determine whether each argument is valid. if the argument is valid, give a proof using the laws of logic. if the argument is invalid, give values for the predicates p and q over the domain {a, b} that demonstrate the argument is invalid. (a) ∃x (p(x) ∧ q(x)) ∴ ∃x q(x) ∧ ∃x p(x) hegg