input question: Question: "If a class is a set, what can it not be?" Context: "The second approach to the problem took as its base the notion of class, and defines a set as a class which belongs to other classes, while a proper class is defined as a class which does not belong to other classes. Under the ZermeloFraenkel approach, the axioms impede the construction of a set of all sets which do not belong to themselves. In contrast, under the von Neumann approach, the class of all sets which do not belong to themselves can be constructed, but it is a proper class and not a set." Answer:???
output answer: proper class

Question: "How did the playing system operate?" Context: "In 1925, 78.26 rpm was chosen as the standard because of the introduction of the electrically powered synchronous turntable motor. This motor ran at 3600 rpm, such that a 46:1 gear ratio would produce 78.26 rpm. In parts of the world that used 50 Hz current, the standard was 77.92 rpm (3,000 rpm with a 77:2 ratio), which was also the speed at which a strobe disc with 77 lines would "stand still" in 50 Hz light (92 lines for 60 Hz). After World War II these records were retroactively known as 78s, to distinguish them from other newer disc record formats. Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records." Answer:
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Answer: electrically

Q: Question: "In what time period did more than 20% of travelers use public transport?" Context: "Melbourne has an integrated public transport system based around extensive train, tram, bus and taxi systems. Flinders Street Station was the world's busiest passenger station in 1927 and Melbourne's tram network overtook Sydney's to become the world's largest in the 1940s, at which time 25% of travellers used public transport but by 2003 it had declined to just 7.6%. The public transport system was privatised in 1999, symbolising the peak of the decline. Despite privatisation and successive governments persisting with auto-centric urban development into the 21st century, there have since been large increases in public transport patronage, with the mode share for commuters increasing to 14.8% and 8.4% of all trips. A target of 20% public transport mode share for Melbourne by 2020 was set by the state government in 2006. Since 2006 public transport patronage has grown by over 20%." Answer:
A: the 1940s

Question: Question: "Why did Bell feel he was vindicated?" Context: "The question of priority for the variable resistance feature of the telephone was raised by the examiner before he approved Bell's patent application. He told Bell that his claim for the variable resistance feature was also described in Gray's caveat. Bell pointed to a variable resistance device in Bell's previous application in which Bell described a cup of mercury, not water. Bell had filed the mercury application at the patent office a year earlier on February 25, 1875, long before Elisha Gray described the water device. In addition, Gray abandoned his caveat, and because he did not contest Bell's priority, the examiner approved Bell's patent on March 3, 1876. Gray had reinvented the variable resistance telephone, but Bell was the first to write down the idea and the first to test it in a telephone." Answer:
Answer: Bell described a cup of mercury, not water

[Q]: Question: "When did the Roman upgrade their fleet?" Context: "After having declined in size following the subjugation of the Mediterranean, the Roman navy underwent short-term upgrading and revitalisation in the late Republic to meet several new demands. Under Caesar, an invasion fleet was assembled in the English Channel to allow the invasion of Britannia; under Pompey, a large fleet was raised in the Mediterranean Sea to clear the sea of Cilician pirates. During the civil war that followed, as many as a thousand ships were either constructed or pressed into service from Greek cities." Answer:
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[A]: following the subjugation of the Mediterranean

Problem: Given the question: Question: "What was lower than the natinoal average?" Context: "In January 2007, the average annual salary in the city was 22,267. This was 1,700 lower than the national average and 3,800 less than the average for the South East." Answer:
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The answer is:
the average annual salary in the city