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. (20) What is the meaning of \"paying for an audience\" and \"paying for content\" in the context of online display and video advertising? (20) In the AB test, a random assignment assured that the control and test groups are at parity. In Card and Krueger's research, where they study the effect of minimum wage change on employment, a random assignment is not possible. How do they still manage a control group in this situation? What are the critical assumptions? . (10) What is the key take-away from the individual assignment of \"scoring model\"? . (10) What are the key differences between branded and non-branded keywords in search engine marketing? Discuss the critical differences at least from two perspectives. (10) The paper \"The Unfavorable Economics of Measuring the Returns to Advertising\" reports that it is empirically challenging to measure the effects of online banner advertising. What is the intuitive interpretation/explanation to this nding