What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y_2, y_2 is a cashier if and only if y_2 is a server. For all y_2, y_2 is a server if and only if y_2 is a cashier.
For all y_2, if y_2 were a cashier, then y_2 is a server. For all y_2, if y_2 were a server, then y_2 is a cashier. For all y_2, if y_2 were a server, then y_2 is a cashier. For all y_2, if y_2 were a cashier, then y_2 is a server.