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_6, x_6 is fast if and only if x_6 will listen to a song. There is at least one x_6 for which if x_6 were fast, then x_6 is listening to a song.
For all x_6, if x_6 were fast, then x_6 is listening to a song can be inferred via the universal biconditional elimination rule. For all x_6, if x_6 listens to a song, then x_6 is fast can be inferred via the universal biconditional elimination rule.