1a. i. State the four (4) types of externalities. (4 marks) ii. Using the following: marginal social cost (MSC), private marginal cost (PMC), marginal social benefit (MSB), and marginal private benefit (MPB), state the conditions which exist in the presence of each of the types of externalities listed in part (i). (4 marks) b. List the five (5) accepted properties/or key attributes of a good tax system. (5 marks) c. Explain what is meant by the "incidence of taxation", and what are the three (3) rules of tax incidence. (4 marks) d. We use average tax rates, rather than the marginal tax rate, to tell whether a tax system is proportional, progressive, or regressive. i. Define the following concepts: a. Marginal tax rate (1 mark) b. Average tax rate (1 mark) ii. State the relationship between the average tax rate and income under each of the three (3) tax systems: progressive, proportional, regressive. (3 marks) e. Explain what is meant by the term "Excess Burden"; and by extension, say what the excess burden of a tax or subsidy has to do with "efficient taxation"