Consider the following premises. u_2 -> s_2. ~s_2. u_2 or s_3. Can we infer s_3 or u from them?
 From u_2 -> s_2, ~s_2 we can infer ~u_2. From u_2 or s_3, ~u_2 we can infer s_3. Finally, from s_3 we can infer s_3 or u. Therefore, the answer is yes.