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: w_1 <-> q_12. w_1. q_12 -> s_1.
w_1 -> q_12 can be inferred via the biconditional elimination rule. q_12 -> w_1 can be inferred via the biconditional elimination rule.