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_17, if x_17 were a sailor, then x_17 is listening to a song. There is at least one x_17 for which x_17 is a writer or x_17 is a musician. For all x_17, if x_17 were a writer, then x_17 is a janitor. For all x_17, x_17 is a sailor. For all x_17, x_17 is a janitor if and only if x_17 is a musician.
For all x_17, x_17 will listen to a song can be inferred via the universal modus ponens rule. For all x_17, if x_17 were a janitor, then x_17 is a musician can be inferred via the universal biconditional elimination rule. For all x_17, if x_17 were a musician, then x_17 is a janitor can be inferred via the universal biconditional elimination rule.