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: Barbara is reading a book or it is not cloudy. It is cloudy or Barbara is not reading a book. It is cloudy if and only if it is overcast. It is not overcast.
If it is cloudy, then Barbara is reading a book can be inferred via the rewriting rule. If Barbara reads a book, then it is cloudy can be inferred via the rewriting rule. If it is cloudy, then it is overcast can be inferred via the biconditional elimination rule. If it is overcast, then it is cloudy can be inferred via the biconditional elimination rule. It is not cloudy can be inferred via the biconditional elimination rule.