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_10 for which if x_10 were a scientist, then x_10 is a cashier. For all x_10, x_10 is a cashier or x_10 is a police officer. For all x_10, if x_10 were a cashier, then x_10 is a scientist. For all x_10, x_10 is not a scientist.
For all x_10, x_10 is not a cashier can be inferred via the universal modus tollens rule. There is at least one x_10 for which x_10 is a scientist if and only if x_10 is a cashier can be inferred via the existential biconditional introduction rule. There is at least one x_10 for which x_10 is a cashier if and only if x_10 is a scientist can be inferred via the existential biconditional introduction rule.