Suppose Katie, Kendra, and Kristen each purchase a particular type of cell phone at a price of $80. Katie's willingness to pay was $100, Kendra's willingness to pay was $95, and Kristen's willingness to pay was $80. Which of the following statements is correct?

Đáp án đúng: "For the three individuals together, consumer surplus amounts to $35." Thặng dư tiêu dùng mỗi người bằng mức sẵn lòng trả trừ giá thực trả: Katie được 100 − 80 = 20, Kendra được 95 − 80 = 15, Kristen được 80 − 80 = 0, cộng lại đúng 35 đô la. "Having bought the cell phone, Kristen is better off than she would have been had she not bought it." sai vì mức sẵn lòng trả của Kristen bằng đúng giá nên thặng dư bằng 0, cô bàng quan giữa mua và không mua. "Had the price of the cell phone been $95 rather than $80, Katie and Kendra definitely would have been buyers and Kristen definitely would not have been a buyer." sai ở chữ chắc chắn: ở giá 95 Kendra chỉ hoà vốn. "The fact that all three individuals paid $80 for the same type of cell phone indicates that each one placed the same value on that cell phone." sai vì cùng trả một giá không có nghĩa cùng định giá.