Consider the following premises. p_21 <-> w_1. u -> w_1. ~p_21. R_28(a_28). forall x_28: R_28(x_28) -> S_28(x_28). Can we infer ~S_28(a_28) from them? If possible, name the inference rules being used at each step.
 From forall x_28: R_28(x_28) -> S_28(x_28) we can infer R_28(a_28) -> S_28(a_28) via universal instantiation. From p_21 <-> w_1, ~p_21 we can infer ~w_1 via biconditional elimination. Finally, from R_28(a_28) -> S_28(a_28), R_28(a_28) we can infer S_28(a_28) via modus ponens, which contradicts ~S_28(a_28). Therefore, the answer is no.