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: For all z, z is a cashier if and only if z is a police officer. There is at least one z for which z is an artist or z is not a police officer.
There is at least one z for which if z were a police officer, then z is an artist can be inferred via the existential rewriting rule. For all z, if z were a cashier, then z is a police officer can be inferred via the universal biconditional elimination rule. For all z, if z were a police officer, then z is a cashier can be inferred via the universal biconditional elimination rule.