What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: forall x: U(x) <-> Q_4(x). forall x: P(x). forall x: Q_4(x) -> U(x). forall x: Q_4(x) -> ~P(x).
forall x: ~Q_4(x) can be inferred via the universal modus tollens rule. forall x: U(x) -> Q_4(x) can be inferred via the universal biconditional elimination rule. forall x: Q_4(x) -> U(x) can be inferred via the universal biconditional elimination rule.