懇請賜教 - 經濟

各位經濟學大大.....我想請問一個很基本的題目

an industry consiss of a large number of firms, each of which has a cost

function of the form with output y C(y)=0.2(y平方+1)+0.3(y平方+2)

if the market price of the commondity is 10, the quantity of y that a firm

would like to supply is

答案是9<y<=11

我知道firm會在p>=AC時生產.....故即是將P>=c(y)/y算出

可是不知怎樣我就是算不出那個答案.....懇請各高手賜教......感激不盡

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