You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
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: Early one morning, more than a hundred years ago, an American inventor called Elias Howe finally fell asleep. He had been working all night on the design of a sewing machine but he had run into a very difficult problem. It seemed impossible to get the thread to run smoothly around the needle. Despite his exhaustion, Howe slept badly. He tossed and turned. Then he had a nightmare He dreamt that he had been caught by terrible savages whose king wanted to kill him and eat him unless he could build a perfect sewing machine. When he tried to do so, Howe ran into the same problem as before. The thread kept getting caught around the needle. The king flew into the cage and ordered his soldiers to kill Howe. They came up towards him with their spears raised. But suddenly the inventor noticed something. There was a hole in the tip of each spear. The inventor awoke from the dream, realizing that he had just found the answer to the problem. Instead of trying to get the thread to run around the needle, he should make a small hole in the center of the needle and have the thread run through it. This was the simple idea that finally made Howe design and build the first really practical sewing machine. Thomas Edison, the inventor of the electric light, said his best ideas came into him in dreams. So did the great physicist Albert Einstein. To appreciate the value of dreams, you have to understand what happens when you are asleep. Even then, a part of your mind is still working. This unconscious , but still active part digests your experiences and goes to work on the problems you have had during the day. However, the unconscious part expresses itself through its own logic and its own language.. It uses strange images which the conscious part may not understand at first. This is why dreams are sometimes called "secret messages to ourselves".
Answer: Making the thread run smoothly around the needle.
Solution:
Which of the following was the main problem for Elias Howe to design a sewing machine?