Consider the following premises. p_4 <-> t_2. ~p_4. t_2 <-> u_3. Can we infer u_3 from them?
 From p_4 <-> t_2, ~p_4 we can infer ~t_2. From t_2 <-> u_3 we can infer u_3 -> t_2. Finally, from u_3 -> t_2, ~t_2 we can infer ~u_3, which contradicts u_3. Therefore, the answer is no.