What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Michael is sleeping if and only if it is cold. It is cold if and only if Mary is taking a plane. If Richard were a doctor, then Mary is taking a plane. Richard is a doctor or Mary is not taking a plane. Michael is not sleeping.
If Mary takes a plane, then Richard is a doctor. If Michael sleeps, then it is cold. If it is cold, then Mary is taking a plane. If it is cold, then Michael is sleeping. If Mary takes a plane, then it is cold. It is not cold.