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: S_3(y) <-> R_4(y). forall y: P(y) -> S_3(y). forall y: S_3(y) -> P(y). forall y: ~R_4(y).
forall y: P(y) <-> S_3(y) can be inferred via the universal biconditional introduction rule. forall y: S_3(y) <-> P(y) can be inferred via the universal biconditional introduction rule. exists y: S_3(y) -> R_4(y) can be inferred via the existential biconditional elimination rule. exists y: R_4(y) -> S_3(y) can be inferred via the existential biconditional elimination rule. exists y: ~S_3(y) can be inferred via the existential biconditional elimination rule.