Consider the following premises. For all x_13, if x_13 were a janitor, then x_13 is climbing a mountain. For all x_13, if x_13 drives a car, then x_13 is climbing a mountain. There is at least one x_13 for which x_13 is not a janitor. For all x_13, x_13 is a janitor if and only if x_13 will climb a mountain. Can we infer the following from them? If we can, name the inference rule being used: For all x_13, x_13 will drive a car.
 From the fact that for all x_13, x_13 is a janitor if and only if x_13 will climb a mountain we can infer that for all x_13, if x_13 climbs a mountain, then x_13 is a janitor via universal biconditional elimination. From the fact that for all x_13, if x_13 were a janitor, then x_13 is climbing a mountain, and that for all x_13, if x_13 climbs a mountain, then x_13 is a janitor we can infer that for all x_13, x_13 is a janitor if and only if x_13 will climb a mountain via universal biconditional introduction. From the fact that for all x_13, x_13 is a janitor if and only if x_13 will climb a mountain, and that there is at least one x_13 for which x_13 is not a janitor we can infer that there is at least one x_13 for which x_13 will not climb a mountain via existential biconditional elimination. Finally, from the fact that for all x_13, if x_13 drives a car, then x_13 is climbing a mountain, and that there is at least one x_13 for which x_13 will not climb a mountain we can infer that there is at least one x_13 for which x_13 will not drive a car via existential modus tollens, which contradicts that For all x_13, x_13 will drive a car. Therefore, the answer is no.