Consider the following premises. R(a_18) -> u. forall x_3: R(x_3). t -> ~u. Can we infer t from them?
 From forall x_3: R(x_3) we can infer R(a_18). From R(a_18) -> u, R(a_18) we can infer u. Finally, from t -> ~u, u we can infer ~t, which contradicts t. Therefore, the answer is no.