Consider the following premises. p -> p_11. q_3 -> u. w_1 -> q_3. u -> s. p_11 -> w_1. Can we infer p -> s from them?
 From p_11 -> w_1, w_1 -> q_3 we can infer p_11 -> q_3. From q_3 -> u, u -> s we can infer q_3 -> s. From p_11 -> q_3, q_3 -> s we can infer p_11 -> s. Finally, from p -> p_11, p_11 -> s we can infer p -> s. Therefore, the answer is yes.