Consider the following premises. ~s. forall x_20: R_20(x_20) and S_20(x_20). s_1 <-> s. Can we infer ~s_1 and R_20(a_20) 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 s_1 <-> s, ~s we can infer ~s_1. From R_20(a_20) and S_20(a_20) we can infer R_20(a_20). Finally, from ~s_1, R_20(a_20) we can infer ~s_1 and R_20(a_20). Therefore, the answer is yes.