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, x_11 is a doctor. For all x_11, x_11 is fast if and only if x_11 is a nurse. For all x_11, if x_11 listens to a song, then x_11 is fast. For all x_11, x_11 will listen to a song or x_11 is a nurse.
For all x_11, if x_11 were fast, then x_11 is a nurse can be inferred via the universal biconditional elimination rule. For all x_11, if x_11 were a nurse, then x_11 is fast can be inferred via the universal biconditional elimination rule.