Question: Who built the 2000/2100 class railcars used in Adelaide, Australia?

Context articles: Queensland Railways 2000 class rail motor
New South Wales 660/760 class railcar
Adelaide Metro
Queensland Railways 1900 class rail motor
Sentetsu Nakeha class railcars
Sentetsu Shiki class railcars
WAGR WCA/WCE class
2000 class railcar
Transwa WDA/WDB/WDC class
Sentetsu Keha class railcars

The 2000 class railcars are a class of self-propelled railcars built by Commonwealth Engineering, Rocklea for the Queensland Railways between 1956 and 1971.
The 660 & 760 Class railcars are a Diesel Multiple Unit train built by the New South Wales Government Railways (NSWGR) and used in the latter stages of their life by CityRail, primarily on its Hunter Valley line.
 The trains have since been phased out in favour of the newer Endeavour railcar model.
 The 660/760 railcars were converted by NSWGR from earlier 600/700 Class vehicles between 1973 to 1975.
Adelaide Metro is the public transport system of Adelaide, the capital city of South Australia.
 It is intermodal system offering an integrated network of bus, tram, and train service throughout the metropolitan area to 63 million riders annually, with an average daily ridership of 33,000 people.
 The system has evolved heavily over the past fifteen years, and patronage increased dramatically during the 2014–15 period, a 5.5 percent increase on the 2013 figures due to electrification of frequented lines.
The 1900 class railcars are a class of self-propelled railcars built by Commonwealth Engineering, Granville for the Queensland Railways in 1956.
The Nakeha (Japanese ナゲハ, Korean 혀게하) class railcars were a group of 3rd class narrow-gauge petrol-powered railcars of the Chosen Government Railway ("Sentetsu").
 There were two classes of such railcars, one built in Japan and one built in Korea.
 After Liberation, they all remained in the South, where they were operated by the Korean National Railroad; none were preserved.
The Shiki or Sigeu (Japanese シキ, Korean 시그) class railcars were a class of 3rd class steam railcars of the Chosen Government Railway ("Sentetsu").
 There were two classes of such railcars, one built in Japan and one built in the United Kingdom.
The WAGR WCA class railcars and WCE class trailers were built by Comeng, Granville for the Western Australian Government Railways in 1971 to operate the new "Prospector" service between East Perth and Kalgoorlie.
 At the time of their construction the WCA class units were the longest and fastest diesel railcars in the world.
The 2000/2100 class were a class of diesel railcars operated by Adelaide Metro.
 They were built by Comeng, Granville in 1979-1980.
The Transwa WDA/WDB/WDC class are a class of railcars built by United Goninan, Broadmeadow for Transwa in 2004/05 to replace the WAGR WCA/WCE class railcars on the "AvonLink" and "Prospector" services in Australia.
 They are capable of high-speed operation.
The Keha (Japanese ケハ, Korean 게하) class railcars were a group of 3rd class petrol-powered railcars of the Chosen Government Railway ("Sentetsu").
 There were five types of such railcars, built in Japan and Korea.
 The exact classification and numbering of these railcars is not certain; certain is only that their type designation was Keha.