The Customer class

class Client : public Active_Customer {
public:
    Door *entrance_door,*exit_door;
    Counter *visited_counter;
    Cashier *used_cashier;
    int nb_articles;
public:
    Client(Time t) : Active_Customer(t) { };
protected:
    void body(){
      sync entrance_door->use();
      sync visited_counter->take(nb_article);
      sync used_cashier->pay(nb_article);
      sync exit_door->use();
    };
};