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: s_3 -> u_1. u_1 -> p_2. ~s_3. p_2 -> s_3.
~p_2 can be inferred via the modus tollens rule. s_3 -> p_2 can be inferred via the transitivity rule. u_1 -> s_3 can be inferred via the transitivity rule. p_2 -> u_1 can be inferred via the transitivity rule.