What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all z, if z writes a letter, then z is a taxi driver. For all z, if z goes running, then z is taking a plane. For all z, if z were a taxi driver, then z is running. There is at least one z for which z will take a plane if and only if z will write a letter.
For all z, if z writes a letter, then z is running. For all z, if z were a taxi driver, then z is taking a plane. There is at least one z for which if z takes a plane, then z is writing a letter. There is at least one z for which if z writes a letter, then z is taking a plane.