Consider the following premises. There is at least one y_1 for which if y_1 takes a plane, then y_1 is a mechanic. For all y_1, if y_1 were a mechanic, then y_1 is a politician. For all y_1, if y_1 were a politician, then y_1 is taking a plane. For all y_1, y_1 will take a plane. Can we infer the following from them? For all y_1, y_1 is not a mechanic.
 From the fact that for all y_1, if y_1 were a mechanic, then y_1 is a politician, and that for all y_1, if y_1 were a politician, then y_1 is taking a plane we can infer that for all y_1, if y_1 were a mechanic, then y_1 is taking a plane. From the fact that for all y_1, if y_1 were a mechanic, then y_1 is taking a plane, and that there is at least one y_1 for which if y_1 takes a plane, then y_1 is a mechanic we can infer that there is at least one y_1 for which y_1 is a mechanic if and only if y_1 will take a plane. From the fact that there is at least one y_1 for which y_1 is a mechanic if and only if y_1 will take a plane we can infer that there is at least one y_1 for which if y_1 takes a plane, then y_1 is a mechanic. Finally, from the fact that there is at least one y_1 for which if y_1 takes a plane, then y_1 is a mechanic, and that for all y_1, y_1 will take a plane we can infer that there is at least one y_1 for which y_1 is a mechanic, which contradicts that For all y_1, y_1 is not a mechanic. Therefore, the answer is no.