What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one z for which if z were an office clerk, then z is working. For all z, z is an office clerk if and only if z is a taxi driver. For all z, z will not play tennis. For all z, if z works, then z is playing tennis.
For all z, z will not work. There is at least one z for which if z were an office clerk, then z is playing tennis. For all z, if z were an office clerk, then z is a taxi driver. For all z, if z were a taxi driver, then z is an office clerk.