Consider the following premises. ~q_9. p <-> q_9. u <-> s. u <-> p. Can we infer s from them?
 From p <-> q_9, ~q_9 we can infer ~p. From u <-> p, ~p we can infer ~u. Finally, from u <-> s, ~u we can infer ~s, which contradicts s. Therefore, the answer is no.