關於成本遞減產業 - 經濟

Suppose the calculator industry is a competitive indusrty
of decreasing cost with negative slope demand curve.

A tax of $100 per calculator will, in the long run,

(a) increacing the price of a calculator by $100.
(b) increacing the price of a calculator by less than $100.
(c) increacing the price of a calculator by more than $100.

講義中此題答案是C

我的想法是這樣

decreasing cost of industry 的供給曲線(S)為負斜率

徵從量稅 => S上移(LAC、LMC上移) => 價格上升、廠商產量增加

=>在長期個別廠商有利潤 =>廠商家數增加(產業擴大)

此時由於廠商為decreasing cost of industry,產業擴大 成本減少

是否LAC& LMC&S 會往下移?

這樣的話 最後價格不就不一定會增加超過$100
如果LAC LMC下降很多的話 price是不是會less than $100?

我就卡在這邊 不知道decreasing cost of industry在這邊的影響該怎麼解釋


再請教各位了
感恩感恩....

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