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_5, if x_5 were fast, then x_5 is playing tennis. For all x_5, if x_5 plays tennis, then x_5 is fast. For all x_5, x_5 will not play tennis.
For all x_5, x_5 is not fast can be inferred via the universal modus tollens rule. For all x_5, x_5 is fast if and only if x_5 will play tennis can be inferred via the universal biconditional introduction rule. For all x_5, x_5 will play tennis if and only if x_5 is fast can be inferred via the universal biconditional introduction rule.