Consider the following premises. forall x_8: P_8(x_8) <-> Q_8(x_8). Q_8(g_4) <-> r_3. forall x_8: ~P_8(x_8). Can we infer r_3 from them?
 From forall x_8: P_8(x_8) <-> Q_8(x_8), forall x_8: ~P_8(x_8) we can infer forall x_8: ~Q_8(x_8). From forall x_8: ~Q_8(x_8) we can infer ~Q_8(g_4). Finally, from Q_8(g_4) <-> r_3, ~Q_8(g_4) we can infer ~r_3, which contradicts r_3. Therefore, the answer is no.