Question: Which monorail used to begin the monorail that is a 3.9 mile long monorail mass transit system?
Context: Brownsville Metro, or "B Metro" for short, is a mass transit system based in and serving Brownsville, TX.  It is currently the largest mass transit system in Cameron County and the Rio Grande Valley, TX, and is the only mass transit system in Cameron County, TX.  Brownsville Metro consists of 15 bus routes and two terminals.  Brownsville Metro carries more than 1.5 million passengers a year.  There is only two mass transit systems in the Rio Grande Valley the second being Metro McAllen which only consist of 7 bus routes and one bus terminal respectfully. Patiala State Monorail Trainways (PSMT) was a unique rail-guided, partially road-borne railways system running in Patiala (British India) from 1907 to 1927.  PSMT was the second monorail system in India, after the Kundala Valley Railway, and the only operational locomotive-hauled railway system built using the Ewing System in the world.  The Kundala Valley Railway pre-dated this, also using the Ewing system between 1902 and 1908, although this only used bullocks for haulage.  Following the conversion of the Kundala Valley Railway from a monorail to a narrow gauge railway in 1908, PSMT was the only monorail system in India until its closure in 1927.  These were the only instances of a monorail train system in India, until the Mumbai Monorail was opened on 2 February 2014. Istanbul Monorail is a proposed monorail mass transit system in Istanbul, Turkey.  It will be in use in the first half of 2019. The Mark IV monorail was a design model of straddle-type monorail trains.  The design was developed by legendary Disney Imagineer Bob Gurr.  Ten trains were built by Martin Marietta in 1969 at the cost of about $7 million USD each and they were used on the Walt Disney World Monorail System between 1971 and 1989 before they were replaced by the Mark VI monorail, although a few lasted until 1991.  Sometime between 1991 and 1994 Monorail Coral and Lime (which had been introduced new in 1984) were sold for $3.5 million each, refurbished, and used to begin the Las Vegas Monorail operations.  In 2004 Lime and Coral (now the MGM and Bally) were replaced by fully automated Bombardier MVI 4-car trains. The Strong Republic Transit System was launched to integrate the various rail lines providing public transport in Manila in the Philippines.  The program was initiated by former president Gloria Macapagal-Arroyo on June 14, 2003.  It aimed to provide a "reliable, seamless and integrated mass transit system that would be at par with international standards" through the unification of already-existing rail infrastructure under one transit system and fare structure.  The Manila Light Rail Transit System (LRT-1 and LRT-2), the Manila Metro Rail Transit System (MRT-3) and the Philippine National Railways (PNR) Northrail and Southrail lines were covered by the SRTS project.  The project has not been mentioned by the Benigno Aquino III and Rodrigo Duterte administrations, which currently concentrates on the extensions of LRT-1 and LRT-2 and the construction of MRT-7, although his administration may continue the stalled Northrail project in a reconfigured way. The Moscow Monorail (Russian: Московский монорельс ) is a 4.7 km long monorail line located in the North-Eastern Administrative Okrug of Moscow, Russia.  It runs from the Timiryazevskaya metro station to Sergeya Eisensteina street.  The monorail line currently has six stations.  Planning of the monorail in Moscow started in 1998.  This was a unique project for Russian companies, which did not have prior experience in building monorails.  6,335,510,000 rubles (about US $240 million) were spent by the city of Moscow on the monorail construction. Kozhikode Light Metro is a proposed mass rapid transport system (MRTS) for the city of Kozhikode (Calicut), in India.  In 2010, the State government explored the possibility of implementing a metro rail project for Kozhikode city and its suburbs.  The proposal was to have a corridor connecting the Karipur Airport to the Kozhikode Medical College Hospital through the heart of the city.  An inception report was submitted by a Bangalore-based consultant, Wilber Smith, on the detailed feasibility study on the prospect of implementing the Mass Rapid Transport System (MRTS) and Light Rail Transit System (LRTS) in the city.  However, the project has been scrapped to be replaced by Kozhikode Monorail project.  The State Cabinet then decided to form a special purpose vehicle (SPV) to implement monorail projects in Kozhikode and Thiruvananthapuram, and administrative sanction was given in October 2012.  The state government issued orders entrusting the Thiruvananthapuram Monorail project to the KMCL on 26 November 2012.  The government had handed over the Kozhikode Monorail project to the KMCL prior to that.  On 12 June 2013, the State Cabinet gave clearance for an agreement to be signed between KMCL and DMRC, that would make the latter the general consultant for the monorail projects in Kozhikode and Thiruvananthapuram.  The DMRC will receive a consultancy fee of 3.25% of the 55.81 billion ( 35.90 billion for Thiruvananthapuram and 19.91 billion for Kozhikode).  The agreement was signed on 19 June 2013.  However, due to cost overrun and the cold response from the bidders the project was put on hold.  Bombardier Transportation was the only bidder for the project.  The project was later scrapped and Light metro was proposed. The Colombo Monorail is a proposed monorail system to be built in Colombo, Sri Lanka.  The project is estimated to cost US$1.3 billion.  Construction was proposed to begin in 2Q 2015.  However a Japanese JICA transportation master plan for Colombo did not recommend a Monorail as a priority and recommended a Bus Rapid Transit (BRT) , Railway electrification an overhead light rail system instead.  A separate study by the Ministry of Megapolis and Western development (see below for more information) also revealed that a Light Rail system is much more feasible than Monorail and decided to go with a Light Rail system, electrified railway system and an Inland water transport ( a brand new boat/ferry service that utilises Colombo’s historic canal network) under the Western Region Megapolis project. The Las Vegas Monorail is a 3.9 mi monorail mass transit system located adjacent to the Las Vegas Strip, in Clark County, Nevada, United States.  It connects several large casinos in the unincorporated communities of Paradise and Winchester, and does not enter the City of Las Vegas.  It is owned and operated by the Las Vegas Monorail Company.  In 2013, total annual ridership was roughly 4.2 million, down from a pre-Great Recession peak of 7.9 million in 2007.  The monorail is a registered not-for-profit corporation, allowed under Nevada law since the monorail provides a public service.  The State of Nevada assisted in bond financing, but no public money was used in construction. The Bangkok Mass Transit System, commonly known as the BTS or the Skytrain (Thai: รถไฟฟ้า rtgs: "rot fai fa" ), is an elevated rapid transit system in Bangkok, Thailand.  It is operated by Bangkok Mass Transit System PCL (BTSC) under a concession granted by the Bangkok Metropolitan Administration (BMA).  The system consists of 35 stations along two lines: the Sukhumvit Line running northwards and eastwards, terminating at Mo Chit and Samrong respectively, and the Silom Line which serves Silom and Sathon Roads, the central business district of Bangkok, terminating at National Stadium and Bang Wa.  The lines interchange at Siam Station and have a combined route length of 37.6 km .  The system is formally known as the Elevated Train in Commemoration of HM the King's 6th Cycle Birthday (รถไฟฟ้าเฉลิมพระเกียรติ 6 รอบ พระชนมพรรษา ).
Answer: Mark IV monorail