Consider the following premises. ~u_2. u_2 or w. w_4. p_19. Can we infer ~w from them? If possible, name the inference rules being used at each step.
 From p_19, w_4 we can infer p_19 and w_4 via conjunction. Finally, from u_2 or w, ~u_2 we can infer w via disjunctive syllogism, which contradicts ~w. Therefore, the answer is no.