consumer surplus - 經濟

學校midterm題目

Nick can purchase each milkshake for $2.

For the first milkshake purchased Nick is willing to pay $4,

for the second milkshake $3,

for the third milkshake $2 and for the fourth milkshake $1.

What is the value of Nick's consumer surplus?


我的想法:價格線以上 跟demand curve以下的面積
不是3 x 3 / 2嗎?

為什麼答案是3?

謝謝!

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