What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: There is at least one z for which z will take a plane if and only if z is a doctor. For all z, if z takes a plane, then z is a doctor.
There is at least one z for which if z takes a plane, then z is a doctor can be inferred via the existential biconditional elimination rule. There is at least one z for which if z were a doctor, then z is taking a plane can be inferred via the existential biconditional elimination rule.