Consider the following premises. s -> q. p_11 -> s. q -> r_3. u or ~r_3. Can we infer p_11 -> u from them?
 From p_11 -> s, s -> q we can infer p_11 -> q. From p_11 -> q, q -> r_3 we can infer p_11 -> r_3. From u or ~r_3 we can infer r_3 -> u. Finally, from p_11 -> r_3, r_3 -> u we can infer p_11 -> u. Therefore, the answer is yes.