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