For the ZYX Company, the ER Diagram is shown below. Review it and answer the question below.

EMPLOYEE entity is related to the CUSTOMER entity using relationships 'Serves' and 'SignsUp'. For both relationships, the cardinality on the EMPLOYEE entity side is $||.$ For the 'Serves' relationship, the cardinality on the CUSTOMER entity side is $0|.$ For the 'SignsUp' relationship, the cardinality on the CUSTOMER entity side is $0<.$ EMPLOYEE entity has three attributes: EmpID $($unique$),$ OfficePhoneNumber $($optional$),$ and CellPhoneNumber $($multiple$).$ CUSTOMER entity has three attributes: CustID $($unique$),$ CustAge $($derived$),$ and CustBDate. CUSTOMER entity is related to itself using the relationship 'Refers'. On one side of the 'Refers' relationship, the cardinality is $0|,$ while on the other side, the cardinality is o$<.$

Which of the following is NOT true according to the ZYX Company ER diagram?

Each employee is serving a unique customer

Each customer has a unique employee serving him or her

Each customer has a unique CustID

Each employee has a unique EmpID