What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If David were a taxi driver, then Jessica is sleeping. Thomas is not happy. Thomas is happy if and only if David is a taxi driver. If Jessica sleeps, then David is a taxi driver.
David is a taxi driver if and only if Jessica is sleeping. Jessica is sleeping if and only if David is a taxi driver. If Thomas were happy, then David is a taxi driver. If David were a taxi driver, then Thomas is happy. David is not a taxi driver.