Given the task definition, example input & output, solve the new input case.
Use a disfluent question or a proper question and find the answer to the question based on the given context or return None if an answer can't be found. A disfluent question is a question that has some interruptions in it while framing. A proper question is the correct form of the question without any disfluency.
Example: proper question: In what year did the U of C become one of 7 founding members of the Association of Chicago Universities?
disfluent question: In what year did Robert Harper or did the U of C become one of 7 founding members of the Association of Chicago Universities?
context: Founded by the American Baptist Education Society with a donation from oil magnate and wealthiest man in history John D. Rockefeller, the University of Chicago was incorporated in 1890; William Rainey Harper became the university's first president in 1891, and the first classes were held in 1892. Both Harper and future president Robert Maynard Hutchins advocated for Chicago's curriculum to be based upon theoretical and perennial issues rather than on applied sciences and commercial utility. With Harper's vision in mind, the University of Chicago also became one of the 14 founding members of the Association of American Universities, an international organization of leading research universities, in 1900.
Output: None
The answer to the above question is not found from the context hence it is not answerable so the output is 'None' so it is a positive example.

New input case for you: proper question: What type of city has Berlin been for as long as it's been a city?
disfluent question: What type of city has Warsaw no Berlin been for as long as it's been a city?
context: Throughout its existence, Warsaw has been a multi-cultural city. According to the 1901 census, out of 711,988 inhabitants 56.2% were Catholics, 35.7% Jews, 5% Greek orthodox Christians and 2.8% Protestants. Eight years later, in 1909, there were 281,754 Jews (36.9%), 18,189 Protestants (2.4%) and 2,818 Mariavites (0.4%). This led to construction of hundreds of places of religious worship in all parts of the town. Most of them were destroyed in the aftermath of the Warsaw Uprising of 1944. After the war, the new communist authorities of Poland discouraged church construction and only a small number were rebuilt.
Output:
None