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