Consider the following premises. r -> u_1. r_8 -> r. u_1 -> r_8. r -> r_8. Can we infer r <-> r_8 from them?
 From r -> u_1, u_1 -> r_8 we can infer r -> r_8. From r_8 -> r, r -> r_8 we can infer r_8 <-> r. From r_8 <-> r we can infer r_8 -> r. Finally, from r -> r_8, r_8 -> r we can infer r <-> r_8. Therefore, the answer is yes.