Consider the following premises. ~p_12. ~s_4 <-> w. p_12 <-> s_4. Can we infer ~w from them?
 From p_12 <-> s_4, ~p_12 we can infer ~s_4. From ~s_4 <-> w we can infer ~s_4 -> w. Finally, from ~s_4 -> w, ~s_4 we can infer w, which contradicts ~w. Therefore, the answer is no.