Consider the following premises. ~p or u. w_1 -> w_4. u -> w_4. p or w_1. Can we infer ~w_4 from them?
 From p or w_1, ~p or u we can infer w_1 or u. Finally, from w_1 -> w_4, u -> w_4, w_1 or u we can infer w_4, which contradicts ~w_4. Therefore, the answer is no.