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_9 for which x_9 will not drive a car. For all x_9, x_9 is fast if and only if x_9 will drive a car. For all x_9, if x_9 were a police officer, then x_9 is fast. For all x_9, if x_9 were fast, then x_9 is a police officer.
For all x_9, x_9 is a police officer if and only if x_9 is fast can be inferred via the universal biconditional introduction rule. For all x_9, x_9 is fast if and only if x_9 is a police officer can be inferred via the universal biconditional introduction rule. For all x_9, if x_9 were fast, then x_9 is driving a car can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 drives a car, then x_9 is fast can be inferred via the universal biconditional elimination rule. There is at least one x_9 for which x_9 is not fast can be inferred via the existential biconditional elimination rule.