Consider the following premises. u. r_4 or ~w_2. w_2. Can we infer r_4 and u from them?
 From r_4 or ~w_2 we can infer w_2 -> r_4. From w_2 -> r_4, w_2 we can infer r_4. Finally, from r_4, u we can infer r_4 and u. Therefore, the answer is yes.