Consider the following premises. Patricia is not running. Patricia is running if and only if Susan is bored. For all y_3, y_3 is a police officer if and only if y_3 is bored. Can we infer the following from them? If we can, name the inference rule being used: Susan is not a police officer.
 From the fact that for all y_3, y_3 is a police officer if and only if y_3 is bored we can infer that Susan is a police officer if and only if Susan is bored via universal instantiation. From the fact that Patricia is running if and only if Susan is bored, and that Patricia is not running we can infer that Susan is not bored via biconditional elimination. Finally, from the fact that Susan is a police officer if and only if Susan is bored, and that Susan is not bored we can infer that Susan is not a police officer via biconditional elimination. Therefore, the answer is yes.