Consider the following premises. p -> u. r_1 -> p_4. r_4 -> p. u -> r_1. Can we infer r_4 -> p_4 from them?
 From u -> r_1, r_1 -> p_4 we can infer u -> p_4. From r_4 -> p, p -> u we can infer r_4 -> u. Finally, from r_4 -> u, u -> p_4 we can infer r_4 -> p_4. Therefore, the answer is yes.