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_10, if x_10 sleeps, then x_10 is a police officer. For all x_10, if x_10 were a police officer, then x_10 is sleeping. If Richard were poor, then Charles is sleeping. For all x_10, x_10 is not a police officer.
For all x_10, x_10 will not sleep can be inferred via the universal modus tollens rule. For all x_10, x_10 will sleep if and only if x_10 is a police officer can be inferred via the universal biconditional introduction rule. For all x_10, x_10 is a police officer if and only if x_10 will sleep can be inferred via the universal biconditional introduction rule.