Problem 7. After Croatia joined the EU in 2013, European Union (EU) enlargement halted. Balkan states Albania, Bosnia-Herzegovina, Kosovo, Montenegro, North Macedonia and Serbia are eager to join the union and continue working on meeting the political and economic requirements for many years. Turkey's application has been in progress for a long time too. Recently, Ukraine, Moldova and Georgia joined the lot of countries applying to join the EU. See, for instance, the articles, "Gerogia and Moldova apply to join EU" (Financial Times, 3 March 2022) and "Ukraine War Forces a Question: How Far East Does Europe Go?" (The New York Times, 26 February 2022), both available on Brightspace. a) Briefly define the concept of free trade area, customs union, common market and economic union in your own words. Give at least one example for each concept. b) Why do so many countries want to join the EU? List and explain some benefits of being part of a free trade area, customs union and political and economic union like the EU. c) What are the requirements these countries have to meet for joining the European Union? What is the economic rationale behind it? d) Some countries within the EU have adopted a common currency: what benefits can be achieved in adopting the Euro? Why have some countries such as Denmark and Sweden chosen to opt out of the single currency