Question: How many survivors were there of the disaster in which the MT Vector oil tanker collided with a ferry?
Context: SS "Atlantic Empress" was a Greek oil tanker that in 1979 collided with the oil tanker "Aegean Captain" in the Caribbean, and eventually sank, having created the fifth largest oil spill on record and the largest ship-based spill. The collision between the oil tanker and the cargo vessel occurred at the Shela River in Sundarbans, Khulna Division, Bangladesh.  The site is near Mongla Port, and is about 100 km from Kolkata Port.  The oil tanker was at anchor at the confluence between the Shela River and the Passur River in dense fog when the cargo vessel collided with it at 5am on December 9, 2014.  The site is in a protected mangrove area, home to rare Irrawaddy and Ganges dolphins. John Fredriksen (born 10 May 1944) is a Norwegian-born oil tanker and shipping magnate, who owns the world's largest oil tanker fleet.  He also has major interests in the offshore driller Seadrill, the fish farming company Marine Harvest, the dry bulk company Golden Ocean Group, and the supply vessel company Deep Sea Supply.  Through his investment companies Hemen Holdings and Meisha, Fredriksen controls the companies Frontline and Golar LNG.  In 2010–2011, Frontline owned 9.6 percent of another large tanker company, Overseas Shipholding Group.  North Atlantic Drilling, Sevan Drilling, and Asia Offshore Drilling are partly owned by Seadrill. The T1 tanker or T1 are a class of sea worthy small tanker ships used to transport fuel oil before and during World War II, Korean War and Vietnam War.  The T1 tanker classification is still in use today.  T1 tankers are about 200 to 250 feet in length and are able to sustain a top speed of about 12 knots.  The hull designation "AO" is used by the US Navy to denote the ship is a T1 oil tanker and "AOG" that the T1 is a gasoline tanker.  The small size allows the T1 to enter just about any sea port or to anchor around a small island, this was very useful during the Pacific War.  The T1 tanker can carry about 48,000 to 280,000 BBLs.  Some T1 tankers were used to transport goods other than oil, a few were used for black oil-crude oil, diesel, chemicals and rarely bulk cargo like grain.  T1 tankers are also called liquid cargo carriers.  The T1 tanker has about a 6,000 to 35,000 DWT of cargo.  The small size also gives the ships short turn around time for repair, cleaning, loading and unloading.  A T1 tanker carrying dirty cargo, like crude oil needs a few weeks of labor to clean before carrying clean cargo.  Most T1 ships during World War II were named after major oil fields. T1 tanker are operated by the US Navy, War Shipping Administration and United States Maritime Commission.  Some T1 were loaned to England in the Lend-Lease program for World War II, after the war most were returned to the USA.  After World War II many of the T1 ships were sold to for civilian use.  Each T1 had emergency life rafts on the boat deck.  The ships had cargo booms and piping to load and unload fuel.  During war time the T1 are armed for protection with deck guns.  A typical ship may have one single 3"/50 dual purpose gun, two 40 mm guns and three single Oerlikon 20 mm cannon.  A T1 at war time normally had a crew of 38 and up to 130.  If operating as a United States Merchant Marine ship, the crew would be a mix of civilian Merchant Marines and United States Navy Armed Guards to man the guns. SS "Papoose was an oil tanker built in 1921 by the Southwestern Shipbuilding & Drydock Company in San Pedro, California as SS "Silvanus for the "Nederlandsch-Indische Tankstoomboot Maatschappij" ("Dutch-Indies Steam Tanker Company").  In 1926 "Silvanus" collided with the tanker "Thomas H. Wheeler" in the Mississippi River, resulting in the death of 26 seamen.  The "Silvanus" was declared a total loss and rebuilt in Beaumont, Texas. The Vector was a Philippine oil tanker that collided with the ferry "Doña Paz" on December 20, 1987 in Tablas Strait, Philippines, resulting in an estimated toll of over 4,000 lives. MT "Mastera" is a Finnish Aframax crude oil tanker operated by Neste Shipping.  She and her sister ship, "Tempera", are the first ships to utilize the double acting tanker (DAT) concept, developed by Aker Arctic, in which the vessel is designed to travel ahead in open water and astern in severe ice conditions.  The two icebreaking tankers are used to transport crude oil year round from the Russian oil terminal in Primorsk to Neste Oil refineries in Porvoo and Naantali. The MV "Doña Paz" was a Philippine-registered passenger ferry that sank after colliding with the oil tanker  on December 20, 1987.  With an estimated death toll of 4,386 people and only 24 survivors, it remains the deadliest peacetime maritime disaster in history. The 2017 Ennore oil spill was an oil spill that occurred outside the Kamarajar Port in Ernavoor, Tamil Nadu, India, on 28 January 2017.  The spill occurred when the outbound empty LPG tanker M.T. BW Maple collided with the inbound fully loaded oil tanker M.T. Dawn Kanchipuram around 04:00 local time. MT "Tempera" is a Finnish Aframax crude oil tanker.  Built at Sumitomo Heavy Industries in Japan in 2002, she was the first ship to utilize the double acting tanker (DAT) concept, developed by Aker Arctic, in which the vessel is designed to travel ahead in open water and astern in severe ice conditions.  "Tempera" and her sister ship "Mastera", built in 2003, were used mainly to transport crude oil, year-round, from the Russian oil terminal in Primorsk to Neste Oil refineries in Porvoo and Naantali.
Answer: 24