6. Marx's theory of exploitation asserts that: A. workers are paid less than the value they contribute to production B. each worker's surplus value is eventually paid out in wages C. when wages are increased, the surplus value extracted from each worker also increases D. as the length of the workday increases, surplus value remains unchanged E. as the length of the working day decreases, surplus value increases 7. Which of the following products is most likely to have an elastic demand? A. toothpicks B. cigarettes C. insulin D. coffee E. automobiles 8. The demand for such products as salt, bread, and electricity tends to be: A. perfectly inelastic B. perfectly elastic C. unit-elastic D. relatively inelastic E. relatively elastic 9. The elasticity of demand for a product is likely to be greater: A. if the product is a "necessity" rather than a "luxury" good B. the greater the amount of time over which producers adjust to a price change C. the smaller the proportion of one's income spent on the product D. the smaller the number of substitute products E. the greater the amount of time over which buyers adjust to a price change