Consider the following premises. t_4 -> u_1. u_1 -> t_4. p_9 <-> u_1. Can we infer ~(t_4 -> p_9) from them?
 From u_1 -> t_4, t_4 -> u_1 we can infer u_1 <-> t_4. From p_9 <-> u_1 we can infer u_1 -> p_9. From u_1 <-> t_4 we can infer t_4 -> u_1. Finally, from t_4 -> u_1, u_1 -> p_9 we can infer t_4 -> p_9, which contradicts ~(t_4 -> p_9). Therefore, the answer is no.