What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If it is windy, then Mary is playing squash. It is windy if and only if Mary is playing squash. Mary is not playing squash.
It is not windy. If it is windy, then Mary is playing squash. If Mary plays squash, then it is windy. It is not windy.