What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If it is late, then Sarah is writing a letter. If Sarah writes a letter, then it is sunny. It is late if and only if it is sunny. Sarah is not writing a letter.
It is not late. If it is late, then it is sunny. If it is late, then it is sunny. If it is sunny, then it is late.