【数学中国推荐】1992-2009年CUMCM优秀论文全收入

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美国的一道题不知怎么做Cobalt, which is not produced in the US, is essential to a number of industries. (Defense accounted for 17% of the cobalt production in 1979.) Most cobalt comes from central Africa, a politically unstable region. The Strategic and Critical Materials Stockpiling Act of 1946 requires a cobalt reserve that will carry the US through a three-year war. The government built up a stockpile in the 1950s, sold most of it off in the early 1970s, and then decided to build it up again in the late 1970s, with a stockpile goal of 85.4 million pounds. About half of this stockpile had been acquired by 1982.
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0 n( p. |2 `  A5 X' _6 D) z& s8 LBuild a mathematical model for managing a stockpile of the strategic metal cobalt. You will need to consider such questions as:

9 o0 F' a: b+ v2 v/ tHow big should the stockpile be?
0 j& D& }+ I( z; ~7 HAt what rate should it be acquired?
What is a reasonable price to pay for the metal?
! a/ h/ Q1 X  pYou will also want to consider such questions as:
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( g; V" X) f) B2 L( gAt what point should the stockpile be drawn down?
4 p6 H8 l$ p) H0 Z5 eAt what rate should it be drawn down?
At what price is it reasonable to sell the metal?
$ y* P% o2 K/ Q( Y' |$ xHow should it be allocated?
  g& E% q) Y/ zUseful Information on Cobalt

The government has projected a need ot 25 million pounds of cobalt in 1985.
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) w% }1 s3 }; |The U.S. has about 100 million pounds of proven cobalt deposits. Production becomes economically feasible when the price reaches $22/lb (as occurred in 1981). It takes four years to get operations rolling, and thsn six million pounds per year can be produced.
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In 1980, 1.2 million pounds of cobalt were recycled, 7% of total consumption.

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顶啊 好东西

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好东西啊。

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大家努力啊！

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十分感谢！！

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