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_5, x_5 is a janitor. For all x_5, if x_5 were a janitor, then x_5 is writing a letter. For all x_5, x_5 is rich or x_5 will not write a letter.
For all x_5, x_5 will write a letter can be inferred via the universal modus ponens rule. For all x_5, if x_5 writes a letter, then x_5 is rich can be inferred via the universal rewriting rule.