What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: It is overcast. If it is overcast, then Sarah is a poet. John is rich or David is sleeping. John is not rich.
Sarah is a poet can be inferred via the modus ponens rule. David is sleeping can be inferred via the disjunctive syllogism rule. It is overcast and John is not rich can be inferred via the conjunction rule. John is not rich and it is overcast can be inferred via the conjunction rule.