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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: Hidden in our subconsciousness   is a perfect mental picture. We see ourselves on a long trip that goes across the continent. We are traveling by train. Out the windows, we think in the passing scene of cars on nearby highways, of children waving at a crossing, of cattle feeding on a distant hillside, of smoke pouring from a power plant, or row upon row of corn and wheat, of flat lands and valleys, of mountains and rolling hills, of city skylines and village halls. But uppermost in our minds is the final destination. On a certain day at a certain hour, we will pull into the station. Bands will be playing and flags waving. Once we get there, so many wonderful dreams will come true and the pieces of our lives will fit together like a completed jigsaw  puzzle. How restlessly we pace the aisles , condemning the minutes for loitering --waiting, waiting, waiting for the station. "When we reach the station, that will be it!" we cry. "When I'm 38." "When I buy a new 450SL Mercdes Benz!" "When I put the last kid through college." "When I have paid off the loan!" "When I get a promotion." "When I reach the age of retirement, I shall live happily ever after! " Sooner or later, we must realize there is no station, no one place to arrive at once and for all. The true joy of life is the trip. The station is only a dream. It constantly outdistances us. "Relish(appreciate) the moment" is a good motto, actually it isn't the burdens of today that drive man mad. It is the regret over yesterday and the fear of tomorrow. Regret and fear are twin thieves who rob us of today. So stop pacing the aisles and counting the miles. Instead, climb more mountains, eat more ice cream, swim more rivers, watch more sunsets, laugh more and cry less. Life must be lived as we go along. Then the station will come soon enough. 
 Answer: To compare it to our life's journey.
Solution:
Why does the author describe the mental picture?