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, x_10 will play tennis. For all x_10, if x_10 were fast, then x_10 is not playing tennis. For all x_10, x_10 is a bartender if and only if x_10 is a police officer. There is at least one x_10 for which x_10 is fast if and only if x_10 is a bartender.
For all x_10, x_10 is not fast can be inferred via the universal modus tollens rule. For all x_10, if x_10 were a bartender, then x_10 is a police officer can be inferred via the universal biconditional elimination rule. There is at least one x_10 for which if x_10 were fast, then x_10 is a bartender can be inferred via the existential biconditional elimination rule. For all x_10, if x_10 were a police officer, then x_10 is a bartender can be inferred via the universal biconditional elimination rule. There is at least one x_10 for which if x_10 were a bartender, then x_10 is fast can be inferred via the existential biconditional elimination rule.