Final answer:
Consumer surplus in a market for a product would be equal to the area under the demand curve if the market price was zero. This scenario would allow consumers to pay nothing while obtaining the full value of what they were willing to pay for a product, which is the definition of consumer surplus.
Step-by-step explanation:
The student asked when consumer surplus in a market for a product would be equal to the area under the demand curve. Consumer surplus is the amount that individuals would have been willing to pay, minus the amount that they actually paid. In economic terms, this would be represented by the area above the market price and below the demand curve.
The correct answer is that consumer surplus in a market for a product would be equal to the area under the demand curve if the market price was zero. At a market price of zero, consumers would be able to purchase the good for free, effectively making the consumer surplus equal to the maximum amount that they were willing to pay for the product, which is shown by the entire area under the demand curve.
The example provided refers to Figure 3.23, where point J on the demand curve shows us that at a price of $90, consumers would have been willing to purchase a quantity of 20 million. The area labeled by F represents the consumer surplus, which is the difference between what consumers would have been willing to pay and what they actually paid, signifying a benefit to the consumers.