Consider the following premises. ~s_4. u -> q_1. q_1 -> r_1. s_4 or u. t. Can we infer r_1 from them?
 From s_4 or u, ~s_4 we can infer u. From u, t we can infer u and t. From u and t we can infer u. From u -> q_1, q_1 -> r_1 we can infer u -> r_1. Finally, from u -> r_1, u we can infer r_1. Therefore, the answer is yes.