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: P_4(x) -> R_4(x). forall x: R_4(x) -> P_4(x). exists x: R_4(x) <-> P_4(x).
forall x: P_4(x) <-> R_4(x) can be inferred via the universal biconditional introduction rule. forall x: R_4(x) <-> P_4(x) can be inferred via the universal biconditional introduction rule. exists x: R_4(x) -> P_4(x) can be inferred via the existential biconditional elimination rule. exists x: P_4(x) -> R_4(x) can be inferred via the existential biconditional elimination rule.