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: q_2 -> u_3. t -> ~u. u_3 -> t. q_2 or ~u_3. u.
~t can be inferred via the modus tollens rule. q_2 -> t can be inferred via the transitivity rule. u_3 -> ~u can be inferred via the transitivity rule. u_3 -> q_2 can be inferred via the rewriting rule.