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 is a server if and only if z is an astronaut. For all z, if z drives a car, then z is an astronaut. For all z, z will drive a car or z is not an astronaut.
For all z, if z were an astronaut, then z is driving a car can be inferred via the universal rewriting rule. There is at least one z for which if z were a server, then z is an astronaut can be inferred via the existential biconditional elimination rule. There is at least one z for which if z were an astronaut, then z is a server can be inferred via the existential biconditional elimination rule.