Consider the following premises. p_1 -> q_13. u. q_13 -> u. u <-> p_1. Can we infer p_1 from them?
 From p_1 -> q_13, q_13 -> u we can infer p_1 -> u. From u <-> p_1 we can infer u -> p_1. From p_1 -> u, u -> p_1 we can infer p_1 <-> u. From p_1 <-> u we can infer u -> p_1. Finally, from u -> p_1, u we can infer p_1. Therefore, the answer is yes.