Consider the following premises. Karen is not a sailor. For all x_2, x_2 is a sailor if and only if x_2 will work. Susan is taking a plane if and only if Karen is working. For all x_12, x_12 is an office clerk if and only if x_12 will take a plane. Can we infer the following from them? If we can, name the inference rule being used: Susan is an office clerk.
 From the fact that for all x_2, x_2 is a sailor if and only if x_2 will work we can infer that Karen is a sailor if and only if Karen is working via universal instantiation. From the fact that for all x_12, x_12 is an office clerk if and only if x_12 will take a plane we can infer that Susan is an office clerk if and only if Susan is taking a plane via universal instantiation. From the fact that Karen is a sailor if and only if Karen is working, and that Karen is not a sailor we can infer that Karen is not working via biconditional elimination. From the fact that Susan is taking a plane if and only if Karen is working, and that Karen is not working we can infer that Susan is not taking a plane via biconditional elimination. Finally, from the fact that Susan is an office clerk if and only if Susan is taking a plane, and that Susan is not taking a plane we can infer that Susan is not an office clerk via biconditional elimination, which contradicts that Susan is an office clerk. Therefore, the answer is no.