Consider the following premises. forall x_20: P_20(x_20). r_4 -> ~q_5. q_5. Can we infer ~r_4 from them?
 From forall x_20: P_20(x_20) we can infer P_20(b_2). Finally, from r_4 -> ~q_5, q_5 we can infer ~r_4. Therefore, the answer is yes.