Consider the following premises. For all x_10, if x_10 sleeps, then x_10 is taking a plane. There is at least one x_10 for which x_10 is fast if and only if x_10 is an office clerk. For all x_10, if x_10 were fast, then x_10 is sleeping. Can we infer the following from them? If we can, name the inference rule being used: For all x_10, the fact that x_10 were an office clerk does not imply that x_10 is taking a plane.
That contradicts the premises. Therefore the answer is no.