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_14 for which if x_14 listens to a song, then x_14 is sleeping. For all x_14, if x_14 sleeps, then x_14 is listening to a song. For all x_14, if x_14 listens to a song, then x_14 is taking a plane. For all x_14, x_14 will take a plane if and only if x_14 will sleep.
For all x_14, if x_14 sleeps, then x_14 is taking a plane can be inferred via the universal transitivity rule. There is at least one x_14 for which x_14 will listen to a song if and only if x_14 will sleep can be inferred via the existential biconditional introduction rule. There is at least one x_14 for which x_14 will sleep if and only if x_14 will listen to a song can be inferred via the existential biconditional introduction rule. For all x_14, if x_14 takes a plane, then x_14 is sleeping can be inferred via the universal biconditional elimination rule. For all x_14, if x_14 sleeps, then x_14 is taking a plane can be inferred via the universal biconditional elimination rule.