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_1, x_1 will sleep if and only if x_1 will make tea. For all x_1, x_1 will listen to a song if and only if x_1 will sleep.
For all x_1, if x_1 sleeps, then x_1 is making tea can be inferred via the universal biconditional elimination rule. For all x_1, if x_1 listens to a song, then x_1 is sleeping can be inferred via the universal biconditional elimination rule. For all x_1, if x_1 makes tea, then x_1 is sleeping can be inferred via the universal biconditional elimination rule. For all x_1, if x_1 sleeps, then x_1 is listening to a song can be inferred via the universal biconditional elimination rule.