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