Consider the following premises. r_3 -> u_1. u_1 or ~t. u_1 -> r_3. Can we infer ~(t -> r_3) from them?
 From r_3 -> u_1, u_1 -> r_3 we can infer r_3 <-> u_1. From r_3 <-> u_1 we can infer u_1 -> r_3. From u_1 or ~t we can infer t -> u_1. Finally, from t -> u_1, u_1 -> r_3 we can infer t -> r_3, which contradicts ~(t -> r_3). Therefore, the answer is no.