Consider the following premises. p_11 <-> u. p_11 -> q. q -> p_11. Can we infer ~(q -> u) from them?
 From p_11 -> q, q -> p_11 we can infer p_11 <-> q. From p_11 <-> q we can infer q -> p_11. From p_11 <-> u we can infer p_11 -> u. Finally, from q -> p_11, p_11 -> u we can infer q -> u, which contradicts ~(q -> u). Therefore, the answer is no.