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_1: R_4(z_1) or ~U(z_1). forall z_1: U(z_1) <-> R_4(z_1).
forall z_1: U(z_1) -> R_4(z_1) can be inferred via the universal rewriting rule. forall z_1: U(z_1) -> R_4(z_1) can be inferred via the universal biconditional elimination rule. forall z_1: R_4(z_1) -> U(z_1) can be inferred via the universal biconditional elimination rule.