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: For all x_6, if x_6 were a writer, then x_6 is not a scientist. For all x_6, x_6 is a writer or x_6 is a bartender. For all x_6, x_6 is a scientist.
For all x_6, x_6 is not a writer can be inferred via the universal modus tollens rule.