The problem: Answer a question about this article:
Whitehead and Russell had thought originally that Principia Mathematica would take a year to complete; it ended up taking them ten years. To add insult to injury, when it came time for publication, the three-volume work was so massive (more than 2,000 pages) and its audience so narrow (professional mathematicians) that it was initially published at a loss of 600 pounds, 300 of which was paid by Cambridge University Press, 200 by the Royal Society of London, and 50 apiece by Whitehead and Russell themselves. Despite the initial loss, today there is likely no major academic library in the world which does not hold a copy of Principia Mathematica.
Who paid to publish Principia Mathematica?
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The answer: Cambridge University Press

The problem: Answer a question about this article:
As of 2007, the total installed capacity of solar hot water systems is approximately 154 thermal gigawatt (GWth). China is the world leader in their deployment with 70 GWth installed as of 2006 and a long-term goal of 210 GWth by 2020. Israel and Cyprus are the per capita leaders in the use of solar hot water systems with over 90% of homes using them. In the United States, Canada and Australia heating swimming pools is the dominant application of solar hot water with an installed capacity of 18 GWth as of 2005.
What country is the leader in the implementation of solar powered hot water systems?
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The answer: China

The problem: Answer a question about this article:
Roman camps followed a standard pattern for defense and religious ritual; in effect they were Rome in miniature. The commander's headquarters stood at the centre; he took the auspices on a dais in front. A small building behind housed the legionary standards, the divine images used in religious rites and in the Imperial era, the image of the ruling emperor. In one camp, this shrine is even called Capitolium. The most important camp-offering appears to have been the suovetaurilia performed before a major, set battle. A ram, a boar and a bull were ritually garlanded, led around the outer perimeter of the camp (a lustratio exercitus) and in through a gate, then sacrificed: Trajan's column shows three such events from his Dacian wars. The perimeter procession and sacrifice suggest the entire camp as a divine templum; all within are purified and protected.
Of what were Roman camps diminutive versions?
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The answer: Rome

The problem: Answer a question about this article:
Charles Pollak (born Karol Pollak), the inventor of the first electrolytic capacitors, found out that the oxide layer on an aluminum anode remained stable in a neutral or alkaline electrolyte, even when the power was switched off. In 1896 he filed a patent for an "Electric liquid capacitor with aluminum electrodes." Solid electrolyte tantalum capacitors were invented by Bell Laboratories in the early 1950s as a miniaturized and more reliable low-voltage support capacitor to complement their newly invented transistor.
In what sort of electrolyte does the oxide layer on an aluminum anode remain stable?
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The answer:
a neutral or alkaline electrolyte