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: q <-> q_12. ~q_12 -> s. ~q. s -> r_1.
~q_12 -> r_1 can be inferred via the transitivity rule. q -> q_12 can be inferred via the biconditional elimination rule. q_12 -> q can be inferred via the biconditional elimination rule. ~q_12 can be inferred via the biconditional elimination rule.