Consider the following premises. u_1 -> p_2. u_1 <-> q_13. q_13. Can we infer p_2 from them?
 From u_1 <-> q_13 we can infer q_13 -> u_1. From q_13 -> u_1, q_13 we can infer u_1. Finally, from u_1 -> p_2, u_1 we can infer p_2. Therefore, the answer is yes.