Answer:
Once the marginal cost of buying extra smoothie exceeds the Marginal benefit derived from consuming extra smoothie, at this point the consumer should stop the purchase.
Step-by-step explanation:
In economic parlance, The marginal cost can be explained as the extra cost incurred by purchasing one more unit of a product. The marginal benefit on the other hand is the extra satisfaction or benefit enjoyed by consuming one more extra unit of a product.
After having figured out the marginal cost and marginal benefit of buying extra smoothie. Once the marginal cost of buying extra smoothie exceeds the Marginal benefit derived from consuming extra smoothie, at this point the consumer should stop the purchase.