Consider the following premises. u_4 -> q. q -> u_4. u_4 <-> s. Can we infer s -> q from them?
 From u_4 <-> s we can infer s -> u_4. From u_4 -> q, q -> u_4 we can infer u_4 <-> q. From u_4 <-> q we can infer u_4 -> q. Finally, from s -> u_4, u_4 -> q we can infer s -> q. Therefore, the answer is yes.