Input: Article: Film speed is used in the exposure equations to find the appropriate exposure parameters. Four variables are available to the photographer to obtain the desired effect: lighting, film speed, f-number (aperture size), and shutter speed (exposure time). The equation may be expressed as ratios, or, by taking the logarithm (base 2) of both sides, by addition, using the APEX system, in which every increment of 1 is a doubling of exposure; this increment is commonly known as a "stop". The effective f-number is proportional to the ratio between the lens focal length and aperture diameter, the diameter itself being proportional to the square root of the aperture area. Thus, a lens set to f/1.4 allows twice as much light to strike the focal plane as a lens set to f/2. Therefore, each f-number factor of the square root of two (approximately 1.4) is also a stop, so lenses are typically marked in that progression: f/1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, etc.

Now answer this question: What is the effective f-number proportional to?

Output: the ratio between the lens focal length and aperture diameter

Input: Article: During the years immediately following the novel's publication, Harper Lee enjoyed the attention its popularity garnered her, granting interviews, visiting schools, and attending events honoring the book. In 1961, when To Kill a Mockingbird was in its 41st week on the bestseller list, it was awarded the Pulitzer Prize, stunning Lee. It also won the Brotherhood Award of the National Conference of Christians and Jews in the same year, and the Paperback of the Year award from Bestsellers magazine in 1962. Starting in 1964, Lee began to turn down interviews, complaining that the questions were monotonous, and grew concerned that attention she received bordered on the kind of publicity celebrities sought. Since the, she declined talking with reporters about the book. She also steadfastly refused to provide an introduction, writing in 1995: "Introductions inhibit pleasure, they kill the joy of anticipation, they frustrate curiosity. The only good thing about Introductions is that in some cases they delay the dose to come. Mockingbird still says what it has to say; it has managed to survive the years without preamble."

Now answer this question: How many weeks did To Kill a Mockingbird remain on the bestsellers list when it won the Pulitzer Prize?

Output: 41

Input: Article: Throughout this period, Saint Helena was an important port of call of the East India Company. East Indiamen would stop there on the return leg of their voyages to British India and China. At Saint Helena ships could replenish supplies of water and provisions, and during war time, form convoys that would sail under the protection of vessels of the Royal Navy. Captain James Cook's vessel HMS Endeavour anchored and resupplied off the coast of St Helena in May 1771, on her return from the European discovery of the east coast of Australia and rediscovery of New Zealand.

Now answer this question: What did ships replenish at Saint Helena?

Output:
water and provisions