Consider the following premises. u <-> q_1. s_4 -> u. q_1 -> s_4. u. Can we infer ~q_1 from them?
 From q_1 -> s_4, s_4 -> u we can infer q_1 -> u. From u <-> q_1 we can infer u -> q_1. From q_1 -> u, u -> q_1 we can infer q_1 <-> u. From q_1 <-> u we can infer u -> q_1. Finally, from u -> q_1, u we can infer q_1, which contradicts ~q_1. Therefore, the answer is no.