Consider the following premises. There is at least one z for which z is an electrician. For all z, if z were sad, then z is a doctor. For all z, if z were curious, then z is a doctor. For all z, if z were an electrician, then z is sad. Can we infer the following from them? If we can, name the inference rule being used: For all z, z is not a doctor.
 From the fact that for all z, if z were an electrician, then z is sad, and that there is at least one z for which z is an electrician we can infer that there is at least one z for which z is sad via existential modus ponens. From the fact that there is at least one z for which z is sad we can infer that there is at least one z for which z is sad or z is curious via existential addition. Finally, from the fact that for all z, if z were sad, then z is a doctor, that for all z, if z were curious, then z is a doctor, and that there is at least one z for which z is sad or z is curious we can infer that there is at least one z for which z is a doctor via existential disjunction elimination, which contradicts that For all z, z is not a doctor. Therefore, the answer is no.