Consider the following premises. For all x_4, x_4 is a taxi driver if and only if x_4 will take a plane. There is at least one x_4 for which if x_4 writes a letter, then x_4 is taking a plane. Can we infer the following from them? If we can, name the inference rule being used: For all x_4, the fact that x_4 writes a letter does not imply that x_4 is a taxi driver.
That contradicts the premises. Therefore the answer is no.