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_4(y). forall y: S_4(y) <-> W(y). forall y: S_4(y) -> W(y).
forall y: S_4(y) -> W(y) can be inferred via the universal biconditional elimination rule. forall y: W(y) -> S_4(y) can be inferred via the universal biconditional elimination rule. exists y: ~W(y) can be inferred via the existential biconditional elimination rule.