Consider the following premises. Richard is a sailor if and only if Michael is driving a car. For all x_12, x_12 will sleep if and only if x_12 will make tea. John is not sleeping. Michael is driving a car if and only if John is making tea. Can we infer the following from them? If we can, name the inference rule being used: Richard is a sailor.
 From the fact that for all x_12, x_12 will sleep if and only if x_12 will make tea we can infer that John is sleeping if and only if John is making tea via universal instantiation. From the fact that John is sleeping if and only if John is making tea, and that John is not sleeping we can infer that John is not making tea via biconditional elimination. From the fact that Michael is driving a car if and only if John is making tea, and that John is not making tea we can infer that Michael is not driving a car via biconditional elimination. Finally, from the fact that Richard is a sailor if and only if Michael is driving a car, and that Michael is not driving a car we can infer that Richard is not a sailor via biconditional elimination, which contradicts that Richard is a sailor. Therefore, the answer is no.