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. Richard is playing squash if and only if it is overcast. If it rains, then Richard is playing squash. If Richard plays squash, then it is raining.
It is raining if and only if Richard is playing squash. Richard is playing squash if and only if it is raining. If Richard plays squash, then it is overcast. If it is overcast, then Richard is playing squash. Richard is not playing squash.