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 Barbara reads a book, then William is not a writer. William is a writer. It is raining if and only if Joseph is a bartender. If it rains, then Barbara is reading a book.
Barbara is not reading a book can be inferred via the modus tollens rule. If it rains, then Joseph is a bartender can be inferred via the biconditional elimination rule. If Joseph were a bartender, then it is raining can be inferred via the biconditional elimination rule.