Consider the following premises. It is late if and only if John is happy. For all x_7, x_7 will take a plane if and only if x_7 is an electrician. John is not happy. It is late if and only if Jessica is taking a plane. Can we infer the following from them? Jessica is not an electrician.
 From the fact that it is late if and only if John is happy, and that John is not happy we can infer that it is not late. From the fact that for all x_7, x_7 will take a plane if and only if x_7 is an electrician we can infer that Jessica is taking a plane if and only if Jessica is an electrician. From the fact that it is late if and only if Jessica is taking a plane, and that it is not late we can infer that Jessica is not taking a plane. Finally, from the fact that Jessica is taking a plane if and only if Jessica is an electrician, and that Jessica is not taking a plane we can infer that Jessica is not an electrician. Therefore, the answer is yes.