Consider the following premises. If Thomas were a poet, then Michael is a server. If Elisabeth drives a car, then Thomas is a poet. Elisabeth is driving a car or Michael is not a server. Can we infer the following from them? If we can, name the inference rule being used: Michael is a server if and only if Thomas is a poet.
 From the fact that Elisabeth is driving a car or Michael is not a server we can infer that if Michael were a server, then Elisabeth is driving a car via rewriting. From the fact that if Michael were a server, then Elisabeth is driving a car, and that if Elisabeth drives a car, then Thomas is a poet we can infer that if Michael were a server, then Thomas is a poet via transitivity. Finally, from the fact that if Michael were a server, then Thomas is a poet, and that if Thomas were a poet, then Michael is a server we can infer that Michael is a server if and only if Thomas is a poet via biconditional introduction. Therefore, the answer is yes.