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 Mary is working. If it is overcast, then it is late. If Mary works, then it is snowing. It is overcast if and only if it is snowing.
If it is late, then it is snowing. If it is overcast, then Mary is working. If it is overcast, then it is snowing. If it snows, then it is overcast.