Consider the following premises. If Linda were a janitor, then Jennifer is drinking water. If Jennifer were bored, then Linda is a janitor. For all x_10, if x_10 drinks water, then x_10 is bored. Can we infer the following from them? If we can, name the inference rule being used: Linda is a janitor if and only if Jennifer is bored.
 From the fact that for all x_10, if x_10 drinks water, then x_10 is bored we can infer that if Jennifer drinks water, then Jennifer is bored via universal instantiation. From the fact that if Linda were a janitor, then Jennifer is drinking water, and that if Jennifer drinks water, then Jennifer is bored we can infer that if Linda were a janitor, then Jennifer is bored via transitivity. Finally, from the fact that if Linda were a janitor, then Jennifer is bored, and that if Jennifer were bored, then Linda is a janitor we can infer that Linda is a janitor if and only if Jennifer is bored via biconditional introduction. Therefore, the answer is yes.