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