Consider the following premises. forall x_11: R_11(x_11) or S_11(x_11). q_4 <-> q_15. ~R_11(a_11) or u. S_11(a_11) -> q_4. ~q_15. Can we infer u from them?
 From q_4 <-> q_15, ~q_15 we can infer ~q_4. From forall x_11: R_11(x_11) or S_11(x_11) we can infer R_11(a_11) or S_11(a_11). From R_11(a_11) or S_11(a_11), ~R_11(a_11) or u we can infer S_11(a_11) or u. From S_11(a_11) -> q_4, ~q_4 we can infer ~S_11(a_11). Finally, from S_11(a_11) or u, ~S_11(a_11) we can infer u. Therefore, the answer is yes.