the total number of pallets handled (i.e. the sum of incoming and outgoing pallets in the distribution center) has been fixed and it is the same in all scenarios. In detail, the arrival rate of loaded pallets from upstream customers is constant and equal to 30 pallets per hour. Furthermore, for the LSP, the estimated ratio between delivered and received palletized loadings is constant and equal to 1.15: this value is not equal to 1 due to picking up activities carried out internally by the LSP;