Consider the following premises. Jennifer is a janitor or Charles is climbing a mountain. If Jennifer were a janitor, then Joseph is a police officer. Joseph is taking a plane if and only if Charles is climbing a mountain. If Joseph were a police officer, then Joseph is taking a plane. Can we infer the following from them? If we can, name the inference rule being used: Joseph is not taking a plane.
 From the fact that Joseph is taking a plane if and only if Charles is climbing a mountain we can infer that if Charles climbs a mountain, then Joseph is taking a plane via biconditional elimination. From the fact that if Jennifer were a janitor, then Joseph is a police officer, and that if Joseph were a police officer, then Joseph is taking a plane we can infer that if Jennifer were a janitor, then Joseph is taking a plane via transitivity. Finally, from the fact that if Jennifer were a janitor, then Joseph is taking a plane, that if Charles climbs a mountain, then Joseph is taking a plane, and that Jennifer is a janitor or Charles is climbing a mountain we can infer that Joseph is taking a plane via disjunction elimination, which contradicts that Joseph is not taking a plane. Therefore, the answer is no.