Question: The Northrop F-15 Reporter was based on a night fighter that included how many mounted M2 Browning machine guns?

full_context: Document 1: North American P-51 Mustang: The North American Aviation P-51 Mustang is an American long-range, single-seat fighter and fighter-bomber used during World War II and the Korean War, among other conflicts. The Mustang was designed in 1940 by North American Aviation (NAA) in response to a requirement of the British Purchasing Commission. The Purchasing Commission approached North American Aviation to build Curtiss P-40 fighters under license for the Royal Air Force (RAF). Rather than build an old design from another company, North American Aviation proposed the design and production of a more modern fighter. The prototype NA-73X airframe was rolled out on 9 September 1940, 102 days after the contract was signed, and first flew on 26 October.
Document 2: Northrop P-61 Black Widow: The Northrop P-61 Black Widow, named for the American spider, was the first operational U.S. warplane designed as a night fighter, and the first aircraft designed to use radar. The P-61 had a crew of three: pilot, gunner, and radar operator. It was armed with four 20 mm (.79 in) Hispano M2 forward-firing cannons mounted in the lower fuselage, and four .50 in (12.7 mm) M2 Browning machine guns mounted in a remote-controlled dorsal gun turret.
Document 3: North American F-82 Twin Mustang: The North American F-82 Twin Mustang was the last American piston-engine fighter ordered into production by the United States Air Force. Based on the P-51 Mustang, the F-82 was originally designed as a long-range escort fighter in World War II. The war ended well before the first production units were operational.
Document 4: Mikoyan-Gurevich MiG-17: The Mikoyan-Gurevich MiG-17 (Russian: Микоян и Гуревич МиГ-17 ; NATO reporting name: Fresco) is a high-subsonic fighter aircraft produced in the USSR from 1952 and operated by numerous air forces in many variants. It is an advanced development of the very similar appearing MiG-15 of the Korean War. The MiG-17 was license-built in China as the Shenyang J-5 and Poland as the PZL-Mielec Lim-6.
Document 5: Lockheed SR-71 Blackbird: The Lockheed SR-71 "Blackbird" is a long-range, Mach 3+ strategic reconnaissance aircraft that was operated by the United States Air Force. It was developed as a black project from the Lockheed A-12 reconnaissance aircraft in the 1960s by Lockheed and its Skunk Works division. American aerospace engineer Clarence "Kelly" Johnson was responsible for many of the design's innovative concepts. During aerial reconnaissance missions, the SR-71 operated at high speeds and altitudes to allow it to outrace threats. If a surface-to-air missile launch was detected, the standard evasive action was simply to accelerate and outfly the missile. The SR-71 was designed with a reduced radar cross-section.
Document 6: Lockheed F-104 Starfighter: The Lockheed F-104 Starfighter is a single-engine, supersonic interceptor aircraft which later became widely used as an attack aircraft. It was originally developed by Lockheed for the United States Air Force (USAF), but became widely used by US Allies around the world, and produced by several other NATO nations. One of the Century Series of fighter aircraft, it was operated by the air forces of more than a dozen nations from 1958 to 2004. Its design team was led by Kelly Johnson, who contributed to the development of the Lockheed P-38 Lightning, Lockheed U-2, Lockheed SR-71 Blackbird and other Lockheed aircraft.
Document 7: Skunk Works: Skunk Works is an official pseudonym for Lockheed Martin's Advanced Development Programs (ADP), formerly called Lockheed Advanced Development Projects. It is responsible for a number of famous aircraft designs, including the U-2, the Lockheed SR-71 Blackbird, the Lockheed F-117 Nighthawk, Lockheed Martin F-22 Raptor, and the Lockheed Martin F-35 Lightning II, which will be used in the air forces of several countries. Its name was taken from the moonshine factory in the comic strip "Li'l Abner". The designation "skunk works" or "skunkworks" is widely used in business, engineering, and technical fields to describe a group within an organization given a high degree of autonomy and unhampered by bureaucracy, with the task of working on advanced or secret projects.
Document 8: Republic F-105 Thunderchief: The Republic F-105 Thunderchief was a supersonic fighter-bomber used by the United States Air Force. The Mach 2 capable F-105 conducted the majority of strike bombing missions during the early years of the Vietnam War; it was the only U.S. aircraft to have been removed from combat due to high loss rates. Originally designed as a single-seat, nuclear-attack aircraft, a two-seat Wild Weasel version was later developed for the specialized Suppression of Enemy Air Defenses (SEAD) role against surface-to-air missile sites. The F-105 was commonly known as the "Thud" by its crews.
Document 9: Kawasaki Ki-61: The Kawasaki Ki-61 "Hien" (飛燕, "flying swallow") is a Japanese World War II fighter aircraft used by the Imperial Japanese Army Air Service. The Japanese Army designation was "Army Type 3 Fighter" (三式戦闘機). Allied pilots initially believed Ki-61s were Messerschmitt Bf 109s and later an Italian aircraft, which led to the Allied reporting name of "Tony", assigned by the United States War Department. It was the only mass-produced Japanese fighter of the war to use a liquid-cooled inline V engine. Over 3,000 Ki-61s were produced. Initial prototypes saw action over Yokohama during the Doolittle Raid on 18 April 1942, and continued to fly combat missions throughout the war.
Document 10: Nord 1500 Noréclair: The Nord 1500 Noréclair was a prototype French twin-engined dive bomber and anti-submarine warfare aircraft built at the end of the Second World War. It would have carried both torpedoes, missiles, and bombs. The aircraft was built in response to a need for a dive bomber and anti-submarine aircraft that could be launched both from land and from an aircraft carrier. The first prototype flew on 29 August 1947. The tests revealed many issues that had to be resolved. Eventually the project was abandoned after being criticized heavily and discovering many problems.
Document 11: Northrop YF-23: The Northrop/McDonnell Douglas YF-23 was an American single-seat, twin-engine stealth fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF's Advanced Tactical Fighter (ATF) competition, battling the Lockheed YF-22 for a production contract. Two YF-23 prototypes were built, nicknamed "Black Widow II" and "Gray Ghost".
Document 12: General Dynamics F-16 Fighting Falcon: The General Dynamics F-16 Fighting Falcon is a single-engine supersonic multirole fighter aircraft originally developed by General Dynamics (now Lockheed Martin) for the United States Air Force (USAF). Designed as an air superiority day fighter, it evolved into a successful all-weather multirole aircraft. Over 4,500 aircraft have been built since production was approved in 1976. Although no longer being purchased by the U.S. Air Force, improved versions are still being built for export customers. In 1993, General Dynamics sold its aircraft manufacturing business to the Lockheed Corporation, which in turn became part of Lockheed Martin after a 1995 merger with Martin Marietta.
Document 13: Northrop JB-1 Bat: The Northrop JB-1 "Bat" was a United States surface-to-surface cruise missile that was a prototype jet-powered flying wing. The United States Army Air Forces MX-543 program was initiated in September 1942 to use US versions of Frank Whittle's jet engine (US-named General Electric J31). The Northrop Corporation was contracted in late 1943, and only 10 JB-1 airframes were built. A manned version was towed for the 1st flight on "August 27, 1943", ["sic"] from Rogers Dry Lake; and a glider version was launched from a rocket-propelled sled and crashed in December 1944. An unmanned JB-1 powered by an improvised General Electric B-1 turbojet with a wing span of 28 ft made its 1st flight from Eglin Field's Santa Rosa Island, Florida, on December 7, 1944, and crashed 400 yards from the rail launcher.
Document 14: Operation Moolah: Operation Moolah was a United States Air Force (USAF) effort during the Korean War to obtain through defection a fully capable Soviet MiG-15 jet fighter. Communist forces introduced the MiG-15 to Korea on November 1, 1950. USAF pilots reported that the performance of the MiG-15 was superior to all United Nations (U.N.) aircraft, including the USAF's newest plane, the F-86 Sabre. The operation focused on influencing Communist pilots to defect to South Korea with a MiG for a financial reward. The success of the operation is disputable since no Communist pilot defected before the armistice was signed on July 27, 1953. However, on September 21, 1953, North Korean pilot Lieutenant No Kum-Sok flew his MiG-15 to the Kimpo Air Base, South Korea, unaware of Operation Moolah.
Document 15: Northrop F-15 Reporter: The Northrop F-15 Reporter (later RF-61) was an American unarmed photographic reconnaissance aircraft. Based on the Northrop P-61 Black Widow night fighter, it was the last piston-powered photo-reconnaissance aircraft designed and produced for the United States Air Force. Though produced in limited quantities, and with a relatively short service life, the F-15's aerial photographs of the Korean Peninsula would prove vital in 1950, when North Korea invaded the south.
ground_truth: four