Consider the following premises. Jennifer is not sad. If Karen were happy, then Jennifer is sad. Karen is not happy if and only if Mary is an electrician. Can we infer the following from them? Mary is an electrician.
 From the fact that if Karen were happy, then Jennifer is sad, and that Jennifer is not sad we can infer that Karen is not happy. From the fact that Karen is not happy if and only if Mary is an electrician we can infer that if Karen were not happy, then Mary is an electrician. Finally, from the fact that if Karen were not happy, then Mary is an electrician, and that Karen is not happy we can infer that Mary is an electrician. Therefore, the answer is yes.