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The Wilson Company's marketing manager has determined that the price elasticity of demand for its product equals 2.2. According to studies she carried out, the relationship between the amount spent by the firm on advertising and its sales is as follows: Advertising Expenditure Sales $100,000 $200,000 $300,000 $400,000 $1.0 million $1.3 million $1.5 million $1.6 million a) If the Wilson Company spends $200,000 on advertising, what is the marginal revenue from an extra dollar of advertising? b) Is $200,000 t