Consider the following premises. s -> q_3. r -> s. q_3 -> r. p_4 <-> q_3. ~s. Can we infer ~p_4 from them?
 From q_3 -> r, r -> s we can infer q_3 -> s. From s -> q_3, q_3 -> s we can infer s <-> q_3. From s <-> q_3, ~s we can infer ~q_3. Finally, from p_4 <-> q_3, ~q_3 we can infer ~p_4. Therefore, the answer is yes.