Consider the following premises. ~r. s_3. s_3 -> u. q_4 <-> r. Can we infer ~q_4 and u from them?
 From s_3 -> u, s_3 we can infer u. From q_4 <-> r, ~r we can infer ~q_4. Finally, from ~q_4, u we can infer ~q_4 and u. Therefore, the answer is yes.