Consider the following premises. For all z_3, if z_3 takes a plane, then z_3 is a nurse. Linda is taking a plane or Linda is not a nurse. Can we infer the following from them? If we can, name the inference rule being used: Linda is a nurse if and only if Linda is taking a plane.
 From the fact that for all z_3, if z_3 takes a plane, then z_3 is a nurse we can infer that if Linda takes a plane, then Linda is a nurse via universal instantiation. From the fact that Linda is taking a plane or Linda is not a nurse we can infer that if Linda were a nurse, then Linda is taking a plane via rewriting. Finally, from the fact that if Linda were a nurse, then Linda is taking a plane, and that if Linda takes a plane, then Linda is a nurse we can infer that Linda is a nurse if and only if Linda is taking a plane via biconditional introduction. Therefore, the answer is yes.