Consider the following premises. For all x_5, x_5 is a janitor if and only if x_5 will make tea. There is at least one x_5 for which if x_5 makes tea, then x_5 is a janitor. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x_5 for which if x_5 were a janitor, then x_5 is making tea.
 From the fact that for all x_5, x_5 is a janitor if and only if x_5 will make tea we can infer that for all x_5, if x_5 were a janitor, then x_5 is making tea via universal biconditional elimination. From the fact that there is at least one x_5 for which if x_5 makes tea, then x_5 is a janitor, and that for all x_5, if x_5 were a janitor, then x_5 is making tea we can infer that there is at least one x_5 for which x_5 will make tea if and only if x_5 is a janitor via existential biconditional introduction. Finally, from the fact that there is at least one x_5 for which x_5 will make tea if and only if x_5 is a janitor we can infer that there is at least one x_5 for which if x_5 were a janitor, then x_5 is making tea via existential biconditional elimination. Therefore, the answer is yes.