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