Consider the following premises. q_8 -> u. p_8 -> u. u -> p_8. p_8 -> q_8. Can we infer ~(p_8 <-> u) from them?
 From p_8 -> q_8, q_8 -> u we can infer p_8 -> u. From u -> p_8, p_8 -> u we can infer u <-> p_8. From u <-> p_8 we can infer u -> p_8. Finally, from p_8 -> u, u -> p_8 we can infer p_8 <-> u, which contradicts ~(p_8 <-> u). Therefore, the answer is no.