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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: How to Tell If Someone Is Happy or Sad on the Phone Scientists have come up with some researches on what makes different types of people"tick". The scientists at the University of Cambridge have developed new mobile phone technology called Emotion Sense that can tell if a caller is happy, angry or sad. Scientists hope to fit the speech recognition system to standard mobile phones and use it to determine emotions--it will also use a GPS tracking system to log where the call is made.  _  The results from the pilot scheme make interesting scientific reading. Among the key revelations (=facts) are that callers feel happier at home and sadder at work. To break it down, scientifically, it shows 45 percent of all emotions produced at home are "happy"and 54 percent of emotions at work are "sad". Meanwhile, people show more "intense"(=nervous) emotions in the evening than they do in the morning. Of course, this could just be because most people feel too tired in the morning to get overly "intense". Eating breakfast and getting to work on time is usually enough of an achievement. Anyway, the Emotion Sense technology has been developed by psychologists  and computer scientists who say it uses speech recognition software and phone sensors  attached to standard smart phones to judge how callers' emotions are changed by everyday factors. The sensors analyze voice samples and these are then divided into five categories: happiness, sadness, fearfulness, anger or neutral---boredom or passivity  would fit into this last category. 
 Answer: Five
Solution:
How many emotions can the sensors tell?