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: Five people are at our table, including myself. I've already learnt a great deal about them in the short time we've been at sea, although we rarely meet except at mealtimes. First of all, there is Dr. Stone. He is a man of about sixty-five, with gray hair and a friendly face. He gave up his work a short while ago and is now traveling round the world before he retires to some quite country village. As a young man, he served for many years as a doctor in the army and visited many countries. He's told us a great deal about the city to which they are going. Then there is "Grandmother". I call her that because her name escapes me. In spite of being a grandmother, she looks remarkable young, no more than fifty. She is on her way to visit a daughter who went to Australia some years ago. Naturally she is very excited at the thought of seeing her again, and her three grandchildren, whom she has never seen. Then there is a man I don't care for very much, the engineer by the name of Barlow. He has been _ in England and is now returning to his work in Singapore. The other person who sits at our table is Mrs. Hunt. I've found out hardly anything about her. She's extremely quiet and rarely talks, except to consult the doctor about children's various illnesses. She is on her way to join her husband in India. 
 Answer: He knows a lot about the city the author is going to visit.
Solution:
What can we know about Mr. Stone?