What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If John plays squash, then David is a doctor. David is a doctor if and only if James is curious. If David were a doctor, then John is playing squash.
John is playing squash if and only if David is a doctor. David is a doctor if and only if John is playing squash. If David were a doctor, then James is curious. If James were curious, then David is a doctor.