 Complete the following phrase:  American racecar driver and constructor Ray Harroun was an early pioneer of the concept of a lightweight single-seater, open-wheel monoposto racecar. After working as a mechanic in the automotive industry, Harroun began competitive professional racing in 1906, winning the AAA National Championship in 1910. He was then hired by the Marmon Motor Car Company as chief engineer, charged with building a racecar intended to race at the first Indianapolis 500, which he went on to win. He developed a revolutionary concept which would become the originator and forefather of the single-seater i.e. monoposto racecar design. Harroun has also been credited by some as pioneering the rear-view mirror which appeared on his 