※ 引述《Expsun (无限燃烧)》之铭言： : 2. A certain wine costs ＄3 a bottle to produce. It improves in taste if : stored properly for a period of time. When it is newly bottled, people are : willing to pay only ＄2 a bottle to drink it. But the amount that people : are willing to pay to drink a bottle of this wine will rise by ＄3 a year : for the next 50 years. Storage costs, not including interest, are ＄.50 : per year. If the interest rate is 5% and the wine is kept by rational : investors, how old will it be when it is drunk and what will be its price : at that time? : a. 50 years old and ＄152 : b. 16 years old and ＄50 : c. 50 years old and ＄153 : d. 20 years old and ＄63 : e. 4 years old and ＄14 (1)酒在第N年卖出时的售价是2+3N，现值则为(2+3N)*D^N D=1/(1+r) (2)酒的生产成本是3 (3)酒在第N年卖出，总储藏成本为0.5*D+0.5*D^2+...+0.5*D^N 酒的价值即为 (1)-(2)-(3) 这一题就是解出一个使酒的价值最高的N值 N应该介於16-17之间 --

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