Consider the following premises. u_2. p_15 -> r. r -> w. q_15 -> r. p_15 or q_15. Can we infer ~w from them?
 From p_15 -> r, q_15 -> r, p_15 or q_15 we can infer r. Finally, from r -> w, r we can infer w, which contradicts ~w. Therefore, the answer is no.