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