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 Robert is a nurse. If Richard plays tennis, then John is drinking water. If Robert were a nurse, then Richard is playing tennis. John is drinking water if and only if it is overcast.
If it is overcast, then Richard is playing tennis. If Robert were a nurse, then John is drinking water. If John drinks water, then it is overcast. If it is overcast, then John is drinking water.