Consider the following premises. r or p_3. u or ~r. p_3 <-> u. Can we infer u from them?
 From u or ~r we can infer r -> u. From p_3 <-> u we can infer p_3 -> u. Finally, from r -> u, p_3 -> u, r or p_3 we can infer u. Therefore, the answer is yes.