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: exists y: P(y) <-> Q_1(y). forall y: Q_1(y) <-> S_4(y). forall y: S_4(y) or P(y).
forall y: Q_1(y) -> S_4(y) can be inferred via the universal biconditional elimination rule. exists y: P(y) -> Q_1(y) can be inferred via the existential biconditional elimination rule. forall y: S_4(y) -> Q_1(y) can be inferred via the universal biconditional elimination rule. exists y: Q_1(y) -> P(y) can be inferred via the existential biconditional elimination rule.