What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If Sarah were fast, then John is writing a letter. Sarah is not playing tennis. John is writing a letter if and only if Sarah is playing tennis. Linda is driving a car.
Sarah is not playing tennis and Linda is driving a car. Linda is driving a car and Sarah is not playing tennis. If John writes a letter, then Sarah is playing tennis. If Sarah plays tennis, then John is writing a letter. John is not writing a letter.