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_8, x_8 is a scientist. For all x_8, x_8 is a cashier or x_8 will climb a mountain. For all x_8, if x_8 were a cashier, then x_8 is drinking water. For all x_8, x_8 will not drink water.
For all x_8, x_8 is not a cashier can be inferred via the universal modus tollens rule.