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Which of the following would tend to increase the elasticity of demand for good X? O a new discovery allows firms to produce X at a much lower cost. O All of the choices are correct. O a new product, Y, which can be used in place of X, is introduced. O the percent of a consumer's income spent on good X declines. O both "the percent of a consumer's income spent on good X declines" and "a new product, Y, which can be used in place of X, is introduced"