Consider the following premises. q <-> p_6. s_4 <-> w. p_6 -> s_4. ~w. Can we infer ~q from them?
 From s_4 <-> w, ~w we can infer ~s_4. From p_6 -> s_4, ~s_4 we can infer ~p_6. From q <-> p_6 we can infer q -> p_6. Finally, from q -> p_6, ~p_6 we can infer ~q. Therefore, the answer is yes.