Consider the following premises. s_2 <-> w. u_4 -> q_8. q_8 -> w. w -> u_4. ~s_2. Can we infer ~u_4 from them?
 From u_4 -> q_8, q_8 -> w we can infer u_4 -> w. From s_2 <-> w, ~s_2 we can infer ~w. From u_4 -> w, w -> u_4 we can infer u_4 <-> w. Finally, from u_4 <-> w, ~w we can infer ~u_4. Therefore, the answer is yes.