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: If it is windy, then Charles is a writer. If Charles were a writer, then it is windy. Charles is a writer or it is not windy.
If it is windy, then Charles is a writer can be inferred via the rewriting rule. It is windy if and only if Charles is a writer can be inferred via the biconditional introduction rule. Charles is a writer if and only if it is windy can be inferred via the biconditional introduction rule.