Consider the following premises. ~q_4. w -> r_2. p_9 <-> q_4. r_2 <-> p_9. Can we infer w from them? If possible, name the inference rules being used at each step.
 From p_9 <-> q_4, ~q_4 we can infer ~p_9 via biconditional elimination. From r_2 <-> p_9, ~p_9 we can infer ~r_2 via biconditional elimination. Finally, from w -> r_2, ~r_2 we can infer ~w via modus tollens, which contradicts w. Therefore, the answer is no.