What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z, z is not a doctor. There is at least one z for which z will take a plane if and only if z is a doctor. For all z, z will take a plane if and only if z is an electrician.
For all z, if z takes a plane, then z is an electrician. There is at least one z for which if z takes a plane, then z is a doctor. For all z, if z were an electrician, then z is taking a plane. There is at least one z for which if z were a doctor, then z is taking a plane. There is at least one z for which z will not take a plane.