Consider the following premises. If John works, then Jennifer is a sailor. If Jennifer makes tea, then James is a taxi driver. For all x_15, if x_15 were a sailor, then x_15 is making tea. James is not a taxi driver. Can we infer the following from them? If we can, name the inference rule being used: John is not working.
 From the fact that for all x_15, if x_15 were a sailor, then x_15 is making tea we can infer that if Jennifer were a sailor, then Jennifer is making tea via universal instantiation. From the fact that if John works, then Jennifer is a sailor, and that if Jennifer were a sailor, then Jennifer is making tea we can infer that if John works, then Jennifer is making tea via transitivity. From the fact that if Jennifer makes tea, then James is a taxi driver, and that James is not a taxi driver we can infer that Jennifer is not making tea via modus tollens. Finally, from the fact that if John works, then Jennifer is making tea, and that Jennifer is not making tea we can infer that John is not working via modus tollens. Therefore, the answer is yes.