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