Consider the following premises. If John were an electrician, then Mary is not sad. For all x_17, if x_17 writes a letter, then x_17 is an electrician. For all x_17, if x_17 were an electrician, then x_17 is writing a letter. Thomas is fast. If Thomas were fast, then Mary is sad. Can we infer the following from them? If we can, name the inference rule being used: For all x_17, if x_17 were an electrician, then x_17 is writing a letter.
That is one of the premises. Therefore, the answer is yes.