Consider the following premises. ~u. forall x_7: R_7(x_7) <-> S_7(x_7). r <-> u. r <-> R_7(a_7). Can we infer S_7(a_7) from them?
 From r <-> u, ~u we can infer ~r. From forall x_7: R_7(x_7) <-> S_7(x_7) we can infer R_7(a_7) <-> S_7(a_7). From r <-> R_7(a_7), ~r we can infer ~R_7(a_7). Finally, from R_7(a_7) <-> S_7(a_7), ~R_7(a_7) we can infer ~S_7(a_7), which contradicts S_7(a_7). Therefore, the answer is no.