Answer:
the total cost of producing a good exceeds the costs borne by the producer.
Explanation:
Negative externality or spillover cost means the cost that should be bear by the third part for an economic transaction in which he or she not involved in the agreement.
Like pollution has been created by the factories but the cleaning cost is beared by the society instead of the factory owner
So, here the total cost of generating the goods should be more than the cost bear by the producer