Consider the following premises. p. p_2 -> u_3. ~p_2. u_3 -> p_2. Can we infer u_3 from them?
 From u_3 -> p_2, p_2 -> u_3 we can infer u_3 <-> p_2. Finally, from u_3 <-> p_2, ~p_2 we can infer ~u_3, which contradicts u_3. Therefore, the answer is no.