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 a taxi driver, then z is playing tennis. There is at least one z for which z is a taxi driver if and only if z will drive a car. For all z, if z plays tennis, then z is drinking water.
For all z, if z were a taxi driver, then z is drinking water can be inferred via the universal transitivity rule. There is at least one z for which if z were a taxi driver, then z is driving a car can be inferred via the existential biconditional elimination rule. There is at least one z for which if z drives a car, then z is a taxi driver can be inferred via the existential biconditional elimination rule.