A free-trade zone is by definition “a place where trade is left to happen without tariffs(tax on imports/exports), quotas, or other restrictions”. An example of a free-trade zone is the European Union. There are no tariffs, quotas, or other restrictions placed on trading within the EU countries (they even share a currency). This allows for them to place products at a cheaper price for good quality and still get enough money to grow wealth within the different countries.
Answer:
If Exosphere is not an option, then it would be Thermosphere
