4- [40 points] China is a major producer of grains, such as wheat, corn, and rice. In 2008 the Chinese government, concerned that grain exports were driving up food prices for domestic consumers, imposed a tax on grain exports. a- Draw the graph that describes the market for grain in China. Use this graph as the starting point to answer the following questions. b- How does an export tax affect domestic grain prices in China? Use supply and demand diagram to illustrate your answer. c- How does the export tax affect the welfare of Chinese' consumers, the welfare of Chinese' producers, and government tax revenue? What happens to total surplus in China, as measured by the sum of consumer surplus, producer surplus, and tax revenue? Use supply and demand diagram to illustrate your answer. Your answers should be derived from welfare analysis based on supply and demand model. d- In which of the following scenarios the magnitude of the impact of this tax on the total surplus of the grain market is greater: 1) When grains are a necessary component of Chinese consumers' food baskets, and 2) When Chinese consumers can substitute grains with other food items. Use supply and demand diagram to illustrate your answer. Your answers should be derived from welfare analysis based on supply and demand model