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_9, x_9 is excited or x_9 is a cashier. For all x_9, if x_9 were excited, then x_9 is not a taxi driver. For all x_9, x_9 will climb a mountain. For all x_9, x_9 is a taxi driver.
For all x_9, x_9 is not excited can be inferred via the universal modus tollens rule. For all x_9, x_9 will climb a mountain and x_9 is a taxi driver can be inferred via the universal conjunction rule. For all x_9, x_9 is a taxi driver and x_9 will climb a mountain can be inferred via the universal conjunction rule.