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 y_4, if y_4 sleeps, then y_4 is a police officer. For all y_4, if y_4 were a police officer, then y_4 is a musician. There is at least one y_4 for which y_4 is a musician if and only if y_4 will sleep.
For all y_4, if y_4 sleeps, then y_4 is a musician can be inferred via the universal transitivity rule. There is at least one y_4 for which if y_4 were a musician, then y_4 is sleeping can be inferred via the existential biconditional elimination rule. There is at least one y_4 for which if y_4 sleeps, then y_4 is a musician can be inferred via the existential biconditional elimination rule.