Consider the following premises. forall x_11: W(x_11) <-> S_11(x_11). ~W(a_11). Can we infer ~S_11(a_11) or t from them? If possible, name the inference rules being used at each step.
 From forall x_11: W(x_11) <-> S_11(x_11) we can infer W(a_11) <-> S_11(a_11) via universal instantiation. From W(a_11) <-> S_11(a_11), ~W(a_11) we can infer ~S_11(a_11) via biconditional elimination. Finally, from ~S_11(a_11) we can infer ~S_11(a_11) or t via addition. Therefore, the answer is yes.