Consider the following premises. s_1 -> p_9. s_1 <-> w. p_9 <-> r. ~r. Can we infer ~w from them?
 From p_9 <-> r, ~r we can infer ~p_9. From s_1 -> p_9, ~p_9 we can infer ~s_1. Finally, from s_1 <-> w, ~s_1 we can infer ~w. Therefore, the answer is yes.