6. Short, conceptual questions. Please be brief. (a) What do sigarettes, salt, and grains have in common such that they have used as money at different instances up through history? (b) Mention two important global institutions that were set up after the Bretton Woods meeting. (c) Who was the first economist who pointed out that comparative advantage, and not absolute advantage, was the crucial condition for mutual gains from trade? (d) Why would we like to assess the value of hedging er ante and not ex post? (e) Some argue that crypto currencies, such as bitcoin, are an environmental nightmare" and not a sustainable technology. What is their argument in terms of energy consumption