Final answer:
Consumer surplus is the extra benefit that consumers receive when they are able to purchase a good or service at a price lower than what they are willing to pay. In this case, the consumer surplus of Robert when he consumes 40 ice-creams at Rs. 8 is Rs. 80.
Step-by-step explanation:
Consumer surplus is the extra benefit that consumers receive when they are able to purchase a good or service at a price lower than what they are willing to pay. To calculate consumer surplus, we need to find the area above the market price and below the demand curve. In this case, it means finding the area of the triangle formed by the price of Rs. 8, the quantity of 40 ice-creams, and the demand curve.
To calculate the area of the triangle, we can use the formula:
Consumer Surplus = 0.5 * base * height
In this case, the base would be the quantity of ice-creams, which is 40, and the height would be the difference between the highest price consumers are willing to pay (indicated by the demand curve) and the actual price, which is Rs. 8.
Consumer Surplus = 0.5 * 40 * (12 - 8) = 0.5 * 40 * 4 = 80
Therefore, the consumer surplus of Robert when he consumes 40 ice-creams at Rs. 8 is Rs. 80.