Consider the following premises. forall x_20: P_20(x_20). P_20(g_4) -> t_1. q_10. Can we infer ~t_1 from them?
 From forall x_20: P_20(x_20) we can infer P_20(g_4). From P_20(g_4), q_10 we can infer P_20(g_4) and q_10. From P_20(g_4) and q_10 we can infer P_20(g_4). Finally, from P_20(g_4) -> t_1, P_20(g_4) we can infer t_1, which contradicts ~t_1. Therefore, the answer is no.