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, if z were an astronaut, then z is driving a car. For all z, if z were a server, then z is an astronaut. If Barbara drives a car, then Barbara is a server.
For all z, if z were a server, then z is driving a car can be inferred via the universal transitivity rule.