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 z: U(z) -> R_3(z). exists z: ~U_1(z). forall z: U_1(z) <-> R_3(z).
forall z: U_1(z) -> R_3(z) can be inferred via the universal biconditional elimination rule. forall z: R_3(z) -> U_1(z) can be inferred via the universal biconditional elimination rule. exists z: ~R_3(z) can be inferred via the existential biconditional elimination rule.