Consider the following premises. q_15 -> s. p_15 -> q_15. p_4 <-> s. w_1 or p_15. w_1 -> s. Can we infer p_4 from them?
 From p_15 -> q_15, q_15 -> s we can infer p_15 -> s. From w_1 -> s, p_15 -> s, w_1 or p_15 we can infer s. From p_4 <-> s we can infer s -> p_4. Finally, from s -> p_4, s we can infer p_4. Therefore, the answer is yes.