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: Jessica is not working. If it is cloudy, then Karen is a janitor. If Robert writes a letter, then Jessica is working. Robert is writing a letter or Karen is not a janitor.
Robert is not writing a letter can be inferred via the modus tollens rule. If Karen were a janitor, then Robert is writing a letter can be inferred via the rewriting rule.