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_2 -> s_3. p_9 or w_2. ~p_9. s_3 -> w_2.
w_2 can be inferred via the disjunctive syllogism rule. w_2 <-> s_3 can be inferred via the biconditional introduction rule. s_3 <-> w_2 can be inferred via the biconditional introduction rule.