Consider the following premises. ~S(a_21). forall z_1: S(z_1) <-> Q(z_1). p_4 <-> Q(a_21). p_8 <-> p_4. Can we infer p_4 <-> Q(a_21) from them? If possible, name the inference rules being used at each step.
That is one of the premises. Therefore, the answer is yes.