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, x_6 is fast. There is at least one x_6 for which x_6 is a writer. For all x_6, x_6 will sleep or x_6 will climb a mountain. For all x_6, if x_6 sleeps, then x_6 is not fast.
For all x_6, x_6 will not sleep can be inferred via the universal modus tollens rule. There is at least one x_6 for which x_6 is a writer and x_6 is fast can be inferred via the existential conjunction rule. There is at least one x_6 for which x_6 is fast and x_6 is a writer can be inferred via the existential conjunction rule.