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_2 or t. t -> q_15. q_15 -> t. ~q_15.
~t can be inferred via the modus tollens rule. ~t -> p_2 can be inferred via the rewriting rule. t <-> q_15 can be inferred via the biconditional introduction rule. q_15 <-> t can be inferred via the biconditional introduction rule.