Answer:
15 cartons
Explanation:
The quantity supplied at a price of $3 was 15 cartons. This is technically the total number of cartons that the store gave to the customers, therefore, supplying them with the carton. In this scenario, this number of cartons would also be the quantity demanded since only 15 customers actually wanted to buy the cartons of eggs and there was enough for all of the customers. This would not be the case if the quantity demanded was more than 15 since there were only 30 cartons available to be supplied.
