6. Who proposed Revealed preference theory? A. Wilfred Pareto B. J. Hicks C. Paul A. Samuelson D. All of the above 7. Which concept explains that, when the price of a good falls it appears cheaper to the cosumer given his income as fixed? A. Substitution effect B. Income effect C. Expense effect D. Cheaper effect mepani answer = 0.5 Mark)