“…In addition, when the PU arrival rate is equal to the PU departure rate, this state is considered to be a "medium PU activity" state [10]. According to these definitions, the PU activities (3, 1) and (5, 1) belong to the low PU activity state, the PU activities (1, 1), (3,3), and (5,5) belong to the medium PU activity state, and the PU activities (1, 2), (1,3), (1,4), (1,5), and (1,6) belong to the high PU activity state.…”