Consider the following premises. For all x_3, if x_3 works, then x_3 is taking a plane. For all x_3, x_3 will take a plane if and only if x_3 is an office clerk. There is at least one x_3 for which if x_3 were an office clerk, then x_3 is working. Can we infer the following from them? For all x_3, the fact that x_3 takes a plane does not imply that x_3 is an office clerk.
That contradicts the premises. Therefore the answer is no.