What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If it is overcast, then Mary is writing a letter. If it snows, then it is overcast. If Mary writes a letter, then it is cold. Sarah is playing squash or it is not cold.
If it is overcast, then it is cold. If it snows, then Mary is writing a letter. If it is cold, then Sarah is playing squash.