Consider the following premises. u <-> w_4. q_11 -> w_4. w_4 -> q_11. u -> q_6. ~q_6. Can we infer ~q_11 from them?
 From w_4 -> q_11, q_11 -> w_4 we can infer w_4 <-> q_11. From u -> q_6, ~q_6 we can infer ~u. From u <-> w_4, ~u we can infer ~w_4. Finally, from w_4 <-> q_11, ~w_4 we can infer ~q_11. Therefore, the answer is yes.