What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one y_1 for which if y_1 were a police officer, then y_1 is a politician. For all y_1, y_1 is a politician if and only if y_1 is a police officer.
For all y_1, if y_1 were a politician, then y_1 is a police officer. For all y_1, if y_1 were a police officer, then y_1 is a politician.