Now suppose the u. s. government does not know the demand curve for pollution and, therefore, cannot determine the optimal tax to achieve the desired level of pollution. instead, it auctions off tradable pollution permits. each permit entitles its owner to emit one ton of sulfur dioxide per day. to achieve the socially optimal quantity of pollution, the government auctions off 150 million pollution permits. given this quantity of permits, the price for each permit in the market for pollution rights will be $ .

ans.

heterothermic organisms include those organisms that can switch between homeothermic (having body temperature higher than environment) and poikilothermic (having variation in internal body temperature) strategies.

some migratory birds show heterothermy as they decrease their metabolic rate during cold nights to keep their body temperature low. drop in metabolic rate allows increase in production efficiency of birds that reduces the internal body temperature to make it equal to external cold temperature during cold nights.

thus, the correct answer is 'birds allow their temperature drop in order to increase their production efficiency.'