Consider the following premises. s -> ~R_20(a_20). forall x_20: R_20(x_20) and S_20(x_20). Can we infer ~s or w_4 from them?
 From forall x_20: R_20(x_20) and S_20(x_20) we can infer R_20(a_20) and S_20(a_20). From R_20(a_20) and S_20(a_20) we can infer R_20(a_20). From s -> ~R_20(a_20), R_20(a_20) we can infer ~s. Finally, from ~s we can infer ~s or w_4. Therefore, the answer is yes.