Consider the following premises. ~w. R_13(a) <-> s. s -> w. forall x_13: R_13(x_13) or S_13(x_13). Can we infer S_13(a) from them?
 From forall x_13: R_13(x_13) or S_13(x_13) we can infer R_13(a) or S_13(a). From s -> w, ~w we can infer ~s. From R_13(a) <-> s, ~s we can infer ~R_13(a). Finally, from R_13(a) or S_13(a), ~R_13(a) we can infer S_13(a). Therefore, the answer is yes.