Consider the following premises. It is not late. For all x_18, x_18 will take a plane. It is late if and only if it is snowing. Can we infer the following from them? If we can, name the inference rule being used: It is snowing.
 From the fact that for all x_18, x_18 will take a plane we can infer that Karen is taking a plane via universal instantiation. Finally, from the fact that it is late if and only if it is snowing, and that it is not late we can infer that it is not snowing via biconditional elimination, which contradicts that It is snowing. Therefore, the answer is no.