***In Manchester, a drug used to treat sick cows is leading to the death of many vultures that feed off dead cattle. Before the decrease in the number of vultures, they sometimes used to smash into the windows of cars driving through the mountains, posing a serious threat to the drivers and their passengers. However, the decline of the vulture population has now led to a sharp increase in the population of rats, mongoose and feral dogs which are now the main scavengers of rotting meat. There have been calls for a ban on the drug used to treat the cows. Identify the externalities that are present in this situation. How efficient would the ban be? How would you design an incentive based regulation to attain an efficient outcome?