Consider the following premises. p_4. p -> r. ~p_4 or u_3. u_3 -> r. Can we infer r from them?
 From p_4 we can infer p_4 or p. From p_4 or p, ~p_4 or u_3 we can infer p or u_3. Finally, from p -> r, u_3 -> r, p or u_3 we can infer r. Therefore, the answer is yes.