Question: How long is the river that flows into the extensional sedimentary basin located in the northern part of the South China Sea?

Context paragraphs:
Caldera Basin: Caldera Basin is a sedimentary basin located in the coast of northern Chile west of Copiapó.  The basin has a fill of marine sediments of Late Cenozoic age.  With a north-south extension of 43 km and an east-west width of 20 km the basin occupies an area between the coast and the Chilean Coast Range and between the port of Caldera and the mouth of Copiapó River.  The sedimentary fill rests on metamorphic rocks of Paleozoic age and on plutonic rocks of Mesozoic age.

Rajasthan Basin: The Rajasthan Basin is a sedimentary basin located in the north west part of India.  This sedimentary basin is one of India’s major sources of petroleum and natural gas and has a geographical extent of about 126,000 sqkm .  The Rajasthan Basin unconfirmably lies over a pre-Cambrian basement.  .

Huangling Complex: Huangling Complex represents a group of rock units appear in the middle of Yangtze Block in South China, distributed across Yixingshan, Zigui, Huangling and Yichang counties.  The group of rock involves nonconformity that sedimentary rocks overlie the metamorphic basement.  It is a 73-km long, asymmetrical dome-shaped anticline with axial plane orientating in north-south direction.  It has a steeper west flank and a gentler east flank.  Basically, there are three tectonic units from the anticline core to the rim, including Archean to Paleoproterozoic metamorphic basement, Neoproterozoic to Jurassic sedimentary rocks and Cretaceous fluvial deposit sedimentary cover.  The northern part of the core is mainly tonalite-trondhjemite-gneiss (TTG) and Cretaceous sedimentary rock, it is called the Archean Kongling Complex.  The middle of the core is mainly the Neoproterozoic granitoid.  The southern part of the core is the Neoproterozoic potassium granite.  Two basins are situated on the western and eastern flanks of the core respectively, including the Zigui basin and Dangyang basin.  Both basins are synforms while Zigui basin has a larger extent of folding.  Yuanan Graben and Jingmen Graben are found within Dangyang Basin area.  Huangling Complex is an important area that helps unravel the tectonic history of South China Craton because it has well-exposed layers of rock units from Archean basement rock to Cretaceous sedimentary rock cover due to the erosion of the anticline.

Pearl River (China): The Pearl River, also known by its Chinese name Zhujiang and formerly often known as the Canton River , is an extensive river system in southern China.  The name "Pearl River" is also often used as a catch-all for the watersheds of the Xi ("West"), Bei ("North"), and Dong ("East") rivers of Guangdong.  These rivers are all considered tributaries of the Pearl River because they share a common delta, the Pearl River Delta.  Measured from the farthest reaches of the Xi River, the Pearl River system is China's third-longest river, 2400 km , after the Yangtze River and the Yellow River, and second largest by volume, after the Yangtze.  The 409480 km2 Pearl River Basin (珠江流域 ) drains the majority of Liangguang (Guangdong and Guangxi provinces), as well as parts of Yunnan, Guizhou, Hunan and Jiangxi in China; it also drains northern parts of Vietnam's Northeast Cao Bằng and Lạng Sơn provinces.

Golfo San Jorge Basin: The Golfo San Jorge Basin (Spanish: "Cuenca Golfo San Jorge" ) is a hydrocarbon-rich sedimentary basin located in eastern Patagonia, Argentina.  The basin covers the entire San Jorge Gulf and an inland area west of it, having one half located in Santa Cruz Province and the other in Chubut Province.  The basin has largely developed under condition of extensional tectonics, including rifting.

Salta Basin: Salta Basin or Salta Rift Basin is a sedimentary basin located in the Argentine Northwest.  The basin started to accumulate sediments in the Early Cretaceous (Neocomian) and at present it has sedimentary deposits reaching thicknesses of 5000 m .  The basin contains seven sub-basins: Tres Cruces, Lomas de Olmedo, Metán, Alemanía, Salfity, El Rey, Sey and Brealito.  The basin environment has variously been described as a "foreland rift" and an "intra-continental rift".  The basin developed under conditions of extensional tectonics and rift-associated volcanism.

Los Angeles Basin: The Los Angeles Basin is a sedimentary basin located in southern California, in a region known as the Peninsular Ranges.  The basin is also connected to an anomalous group of east-west trending chain of mountains collectively known as the California Transverse Ranges.  The present basin is a coastal lowland area, whose floor is marked by elongate low ridges and groups of hills that is located on the edge of the Pacific plate.  The Los Angeles Basin, along with the Santa Barbara Channel, the Ventura Basin, the San Fernando Valley, and the San Gabriel Basin, lies within the greater southern California region.  On the north, northeast, and east, the lowland basin is bound by the Santa Monica Mountains and Puente, Elysian, Repetto hills.  To the southeast, the basin is bordered by the Santa Ana mountains and the San Joaquin Hills.  The western boundary of the basin is marked by the Continental Borderland and is part of the onshore portion.  The California borderland is characterized by north-west trending offshore ridges and basins.  The Los Angeles Basin is notable for its great structural relief and complexity in relation to its geologic youth and small size for its prolific oil production.  Yerkes et al. identify 5 major stages of the basin's evolution that begins in the Upper Cretaceous and ends in the Pleistocene.  This basin can be classified as an irregular pull-apart basin accompanied by rotational tectonics during the post-early Miocene.

Pearl River Mouth basin: The Pearl River Mouth basin (PRMB) is an extensional sedimentary basin located in the northern part of the South China Sea.  The basin covers an area of about 175,000 km where the Pearl River meets the South China Sea near Hong Kong.

Tectonics of the South China Sea: The South China Sea Basin is one of the largest marginal basins in Asia.  South China Sea is located to the east of Vietnam, west of Philippines and the Luzon Strait, and north of Borneo.  Tectonically, it is surrounded by the Indochina Block on the west, Philippines Sea plate on the east, Yangtze Block to the north.  A subduction boundary exists between the Philippines Sea Plate and the Asian Plate.  The formation of the South China Sea Basin was closely related with the collision between the Indian Plate and Eurasian Plates.  The collision thickened the continental crust and changed the elevation of the topography from the Himalayan orogenic zone to the South China Sea, especially around the Tibetan Plateau.  The location of the South China Sea makes it a product of several tectonic events.  All the plates around the South China Sea Basin underwent clockwise rotation, subduction and experienced an extrusion process from the early Cenozoic to the Late Miocene.

Yinggehai basin: The Yinggehai-Song Hong Basin is located on the northwest of the South China Sea, between Hainan island and the coast of northern Vietnam.  It is a large extensional pull-part basin in extensional continental marginal setting, developed along the Red River fault zone, which located at the suture of the Indochina Plate and Yangtze Plate (South China Plate).

Supporting paragraphs: Pearl River Mouth basin Pearl River (China)
Answer: 2400 km