請問一題獨佔的最大收益 - 經濟

The following table provides information on the price, quantity, and average
cost for a monopoly. At what price will the firm maximize its profit?
Price Output Average Total Cost
5 0 --
4 4 1
3 8 0.75
2 12 0.75
1 16 0.81
0 20 0.9


答案是3
請問這題是要找mr=mc的地方嗎?
可是產量是給4.8.12要怎麼找邊際阿?
謝謝!!

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