Adama is a French manufacturer of photovoltaic panels. The company has a production plant in Rennes, which supplies four warehouses located in Angers, Bourges, Clermont-Ferrand and Montauban. The warehouses directly supply the installers, grouped, for this purpose, into 10 operative districts spread across the country. The installers belonging to the same operative district are served from a single warehouse. Each installer returns defective photovoltaic panels to the corresponding warehouse; these panels are then sent to a repairing centre located in Poitiers. Model the logistics system of Adama through a directed graph and give a graphical representation of it (hint: the installers of the same operative district are assumed to be concentrated in a unique point).