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_6 -> r_3. r_3 -> p_6. ~p_6.
~r_3 can be inferred via the modus tollens rule. p_6 <-> r_3 can be inferred via the biconditional introduction rule. r_3 <-> p_6 can be inferred via the biconditional introduction rule.