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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: Do you know how to use a mobile phone without being rude to the people around you? Talking during a performance irritates people. If you are expecting an emergency call, sit near the exit doors and set your phone to vibrate . When your mobile phone vibrates, you can leave quietly and let the others enjoy the performance. Think twice before using mobile phones in elevators, museums, churches or other indoor public places--especially enclosed spaces. Would you want to listen to someone's conversation in these places? Worse yet, how would you feel if a mobile phone rang suddenly during a funeral! It happens more often than you think. Avoid these embarrassing situations by making sure your mobile phone is switched off. When eating at a restaurant with friends, don't place your mobile phone on the table. This conveys the message that your phone calls are more important than those around you. Mobile phones have sensitive microphones that allow you to speak at the volume you would on a regular phone. This enables you to speak quietly so that others won't hear the details of your conversations. If you are calling from a noisy area, use your hand to direct your voice into the microphone. Many people believe that they can't live without their mobile phone. Owning a mobile phone definitely makes life more convenient, but limit your conversations to urgent ones and save the personal calls until you are at home.
Answer: Speak in a low voice.
Solution:
What should you do when you need to answer a phone call during a performance?