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 x: Q(x) -> U_4(x). forall x: U_4(x) -> Q(x). exists x: U_4(x) -> Q(x).
forall x: Q(x) <-> U_4(x) can be inferred via the universal biconditional introduction rule. forall x: U_4(x) <-> Q(x) can be inferred via the universal biconditional introduction rule. exists x: U_4(x) <-> Q(x) can be inferred via the existential biconditional introduction rule. exists x: Q(x) <-> U_4(x) can be inferred via the existential biconditional introduction rule.