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: There is at least one x_1 for which if x_1 were fast, then x_1 is a janitor. For all x_1, if x_1 were a writer, then x_1 is fast. For all x_1, x_1 is not a janitor.
There is at least one x_1 for which x_1 is not fast can be inferred via the existential modus tollens rule. There is at least one x_1 for which if x_1 were a writer, then x_1 is a janitor can be inferred via the existential transitivity rule.