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_15, x_15 will not listen to a song. There is at least one x_15 for which x_15 is a police officer if and only if x_15 is a musician. For all x_15, if x_15 were rich, then x_15 is playing squash. For all x_15, if x_15 plays squash, then x_15 is a police officer. For all x_15, x_15 will listen to a song or x_15 is rich.
For all x_15, if x_15 were rich, then x_15 is a police officer can be inferred via the universal transitivity rule. For all x_15, x_15 is rich can be inferred via the universal disjunctive syllogism rule. There is at least one x_15 for which if x_15 were a police officer, then x_15 is a musician can be inferred via the existential biconditional elimination rule. There is at least one x_15 for which if x_15 were a musician, then x_15 is a police officer can be inferred via the existential biconditional elimination rule.