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_11, if x_11 plays tennis, then x_11 is a doctor. For all x_11, if x_11 listens to a song, then x_11 is playing tennis. For all x_11, x_11 will listen to a song if and only if x_11 is a doctor.
For all x_11, if x_11 listens to a song, then x_11 is a doctor can be inferred via the universal transitivity rule. For all x_11, if x_11 listens to a song, then x_11 is a doctor can be inferred via the universal biconditional elimination rule. For all x_11, if x_11 were a doctor, then x_11 is listening to a song can be inferred via the universal biconditional elimination rule.