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In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

Article: There are a lot of public libraries in Britain. These libraries have more than one hundred and fifteen million books, not including those libraries of public schools. Public libraries not only lend books, music records but also help children, patients in hospitals and others to get special play readings, film shows and so on. The first public libraries were founded in about the year 1850. Today's public libraries usually have a reading-room, a lending room and a reference room. The greatest and most famous library in Britain is that of the British Library in London. It was founded in 1973 and has over 10, 000, 000 books. It has nearly every magazine, newspaper and book published in Britain and other parts across the world.
Answer: 10,000,000 or less.
Solution: How many books are there in the British Library?
Why? In the Article, 10,000,000 is mentioned for the number of books available in the British Library, so this is a good question.

New input: Article: Today's word, pan, takes us back to the days of the gold rush in California. On January 24th, 1848, a man named James Wilson Marshall discovered gold in California. The news spread quickly. Thousands rushed west. They traveled on foot, on horseback and by boat to reach the gold fields. By 1849, the great gold rush was on. Towns and cities grew overnight. Throughout California --- in the mountains, along the streams and rivers --- thousands of people searched for gold. Some found areas of mountain rock thick with gold. These men got rich. But such areas were few and quickly claimed by the first men to find them. Others searched for gold in the rivers coming down the mountains. They were after pieces of gold that the rains had washed down from above . The only way to find this gold was by panning. First a gold miner put dirt in a metal pan and added water. Then he shook the pan so that the water would wash the dirt. Slowly, he poured the water out of the pan. If he was a lucky miner, pieces of gold would remain. Across the nation, newspapers carried stories of the gold being found. Each one hoped that the place he claimed panned out well --- had some gold. For many, gold mining did not pan out. For a few, it panned out well. But in time, huge machines were built that could wash many tons of dirt at a time. Panning died out. The word, however, remained in the language. Today, Americans still say, " It panned out well ," when something they have done pleases them. A business, a discovery, a simple event pans out well if it is successful. Unhappily, sometimes things do not pan out. In recent years, the word pan has taken on another meaning. Today, it also means to criticize. How it got this meaning is hard to discover. But the job of a critic is to sometimes pan the work of a writer, artist or singer.
Answer: Because the land of California was fertile at that time.
Solution:
Why did so many people flood to California in 1848?