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: T(y) -> Q_4(y). forall y: Q_4(y) -> T(y). forall y: T(y) -> Q_4(y).
forall y: Q_4(y) <-> T(y) can be inferred via the universal biconditional introduction rule. forall y: T(y) <-> Q_4(y) can be inferred via the universal biconditional introduction rule. exists y: T(y) <-> Q_4(y) can be inferred via the existential biconditional introduction rule. exists y: Q_4(y) <-> T(y) can be inferred via the existential biconditional introduction rule.