Input: Read this: The United States Mint produces Proof Sets specifically for collectors and speculators. Silver Proofs tend to be the standard designs but with the dime, quarter, and half dollar containing 90% silver. Starting in 1983 and ending in 1997, the Mint also produced proof sets containing the year's commemorative coins alongside the regular coins. Another type of proof set is the Presidential Dollar Proof Set where four special $1 coins are minted each year featuring a president. Because of budget constraints and increasing stockpiles of these relatively unpopular coins, the production of new Presidential dollar coins for circulation was suspended on December 13, 2011, by U.S. Treasury Secretary Timothy F. Geithner. Future minting of such coins will be made solely for collectors.
Question: When did the Mint being producing proof sets?

Output: 1983


Input: Read this: Sumerian religion seems to have been founded upon two separate cosmogenic myths. The first saw creation as the result of a series of hieros gami or sacred marriages, involving the reconciliation of opposites, postulated as a coming together of male and female divine beings; the gods. This continued to influence the whole Mesopotamian mythos. Thus in the Enuma Elish the creation was seen as the union of fresh and salt water; as male Abzu, and female Tiamat. The product of that union, Lahm and Lahmu, "the muddy ones", were titles given to the gate keepers of the E-Abzu temple of Enki, in Eridu, the first Sumerian city. Describing the way that muddy islands emerge from the confluence of fresh and salty water at the mouth of the Euphrates, where the river deposited its load of silt, a second hieros gamos supposedly created Anshar and Kishar, the "sky-pivot" or axle, and the "earth pivot", parents in turn of Anu (the sky) and Ki (the earth). Another important Sumerian hieros gamos was that between Ki, here known as Ninhursag or "Lady Sacred Mountain", and Enki of Eridu, the god of fresh water which brought forth greenery and pasture.
Question: Who was the Lady Sacred Mountain?

Output: Ninhursag


Input: Read this: The Scheinergrade (Sch.) system was devised by the German astronomer Julius Scheiner (1858–1913) in 1894 originally as a method of comparing the speeds of plates used for astronomical photography. Scheiner's system rated the speed of a plate by the least exposure to produce a visible darkening upon development. Speed was expressed in degrees Scheiner, originally ranging from 1° Sch. to 20° Sch., where an increment of 19° Sch. corresponded to a hundredfold increase in sensitivity, which meant that an increment of 3° Sch. came close to a doubling of sensitivity.
Question: Approximately how many degrees indicate double the sensitivity? 

Output: an increment of 3° Sch


Input: Read this: Epigenetic changes in eukaryotic biology serve to regulate the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. A single fertilized egg cell, the zygote, gives rise to the many different plant cell types including parenchyma, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis, etc. as it continues to divide. The process results from the epigenetic activation of some genes and inhibition of others.
Question: What process causes changes in plant cells?

Output:
Epigenetic changes