Consider the following premises. For all x, if x were a politician, then x is taking a plane. There is at least one x for which x will take a plane if and only if x is an office clerk. For all x, if x were an office clerk, then x is a politician. Can we infer the following from them? If we can, name the inference rule being used: There is at least one x for which x will take a plane if and only if x is an office clerk.
That is one of the premises. Therefore, the answer is yes.