An assistance system that optimizes the operation of a self-propelled agricultural working machine includes a device for determining working and efficiency parameters of the machine includes an arithmetic logic unit and a display unit. The arithmetic logic unit processes information generated by machine-internal sensor systems, external information and information stored in the arithmetic logic unit. One or more mathematical models describing the working process are stored in the arithmetic logic unit and derive efficiency parameters of the working machine from the available working parameters and, with consideration for monetary interrelationships, determine the opportunity costs of the working process and visualize the opportunity costs in the display unit.