Consider the following premises. r_2 -> R_4(g). forall x_7: R_4(x_7) <-> S_7(x_7). Can we infer ~(r_2 -> S_7(g)) from them?
 From forall x_7: R_4(x_7) <-> S_7(x_7) we can infer R_4(g) <-> S_7(g). From R_4(g) <-> S_7(g) we can infer R_4(g) -> S_7(g). Finally, from r_2 -> R_4(g), R_4(g) -> S_7(g) we can infer r_2 -> S_7(g), which contradicts ~(r_2 -> S_7(g)). Therefore, the answer is no.