I am working on my study guide for my final exam and im not sure my answers are correct. Can someone help me out please?

67. What is absolute and comparative advantage? How do we calculate both?

68. What are exports? Imports?

69. What are the barriers to trade? Why do governments use tariffs and quotas? What is the difference between a protective tariff and a revenue tariff?

70. What are the different types of exchange rates?