Consider the following premises. Sarah is a police officer if and only if Sarah is working. If Barbara were a taxi driver, then Sarah is a police officer. Barbara is a taxi driver. Can we infer the following from them? If we can, name the inference rule being used: Sarah is a police officer.
 From the fact that Barbara is a taxi driver we can infer that Barbara is a taxi driver or Sarah is working via addition. From the fact that Sarah is a police officer if and only if Sarah is working we can infer that if Sarah works, then Sarah is a police officer via biconditional elimination. Finally, from the fact that if Barbara were a taxi driver, then Sarah is a police officer, that if Sarah works, then Sarah is a police officer, and that Barbara is a taxi driver or Sarah is working we can infer that Sarah is a police officer via disjunction elimination. Therefore, the answer is yes.