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 it is snowing. If it snows, then it is overcast. Robert is a cashier or it is overcast. If Robert were a cashier, then it is snowing.
If Robert were a cashier, then it is overcast. It is snowing. It is overcast if and only if it is snowing. It is snowing if and only if it is overcast.