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 z, z is a police officer if and only if z is a musician. There is at least one z for which if z were a musician, then z is a politician. For all z, z is not a police officer. For all z, if z were a politician, then z is a musician.
There is at least one z for which z is a musician if and only if z is a politician can be inferred via the existential biconditional introduction rule. There is at least one z for which z is a politician if and only if z is a musician can be inferred via the existential biconditional introduction rule. For all z, if z were a police officer, then z is a musician can be inferred via the universal biconditional elimination rule. For all z, if z were a musician, then z is a police officer can be inferred via the universal biconditional elimination rule. For all z, z is not a musician can be inferred via the universal biconditional elimination rule.