Consider the following premises. p_1 -> q_1. q_1 -> q_9. p_9 <-> q_9. Can we infer p_1 -> p_9 from them?
 From p_9 <-> q_9 we can infer q_9 -> p_9. From p_1 -> q_1, q_1 -> q_9 we can infer p_1 -> q_9. Finally, from p_1 -> q_9, q_9 -> p_9 we can infer p_1 -> p_9. Therefore, the answer is yes.