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_4: S_4(z_4) <-> S_2(z_4). q_6 -> S_2(b). r -> q_6.
r -> S_2(b) can be inferred via the transitivity rule. forall z_4: S_4(z_4) -> S_2(z_4) can be inferred via the universal biconditional elimination rule. forall z_4: S_2(z_4) -> S_4(z_4) can be inferred via the universal biconditional elimination rule.