What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Barbara is happy. If it is overcast, then it is cold. If it is cold, then it is overcast. It is not overcast. If it is sunny, then it is cold.
It is not cold. Barbara is happy and it is not overcast. It is not overcast and Barbara is happy. It is overcast if and only if it is cold. It is cold if and only if it is overcast.