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_1 -> p_2. q -> p_2. ~q. p_2 -> q.
~p_2 can be inferred via the modus tollens rule. q <-> p_2 can be inferred via the biconditional introduction rule. p_2 <-> q can be inferred via the biconditional introduction rule.