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: p_3 -> t_4. ~s_3. p_3 -> s_3. t_4 -> p_3.
~p_3 can be inferred via the modus tollens rule. t_4 -> s_3 can be inferred via the transitivity rule. p_3 <-> t_4 can be inferred via the biconditional introduction rule. t_4 <-> p_3 can be inferred via the biconditional introduction rule.