Consider the following premises. forall y: S(y) <-> Q(y). u <-> S(c). forall y: ~Q(y). Can we infer u from them? If possible, name the inference rules being used at each step.
 From forall y: S(y) <-> Q(y), forall y: ~Q(y) we can infer forall y: ~S(y) via universal biconditional elimination. From forall y: ~S(y) we can infer ~S(c) via universal instantiation. Finally, from u <-> S(c), ~S(c) we can infer ~u via biconditional elimination, which contradicts u. Therefore, the answer is no.