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: P(x) -> S(x). forall x: S(x) -> P(x). forall x: U(x). forall x: S(x) -> ~U(x).
forall x: ~S(x) can be inferred via the universal modus tollens rule. forall x: P(x) <-> S(x) can be inferred via the universal biconditional introduction rule. forall x: S(x) <-> P(x) can be inferred via the universal biconditional introduction rule.