 Complete the following phrase:  The chassis was named F1 W06 Hybrid to represent the sixth Formula One car that Mercedes had constructed since , while the hybrid was marked to recognize the utilization of fully integrated hybrid power units. The car made its competitive debut at the 2015 Australian Grand Prix, the opening round of the 2015 season. After participating in 18 rounds of Grand Prix racing, the car made its final competition appearance at the season finale race  the 