function return..

im not sure what to return for this function? TourBus& TourBus::startTheTour() const { if (busSizeNumber != 4) { cout << "Cannot start the tour, the bus is not fully boarded!" << endl; } else { cout << "Starting the tour...." << endl; cout << "Passenger List:" << endl; cout << "|Row | Passenger Name | Num |" << endl; cout << "+----+------------------------------------------+-----+" << endl; ticket->display(); cout << "+----+------------------------------------------+-----+" << endl; } return .......; } }