Consider the following premises. ~u_3 -> q_1. ~s. u_3 <-> s. Can we infer q_1 or u_4 from them?
 From u_3 <-> s, ~s we can infer ~u_3. From ~u_3 -> q_1, ~u_3 we can infer q_1. Finally, from q_1 we can infer q_1 or u_4. Therefore, the answer is yes.