Which of the following statements is correct for the case of a downward-sloping demand curve (beyond the first unit of output)?

Which of the following is a true statement regarding the economic growth model's predictions and how it actually affects the real world?

A) The growth model predicts that poor countries will catch up with rich countries, but lower-income industrialized countries are not catching up to higher-income industrialized countries as a group. B) The growth model predicts that poor countries should catch up with rich countries, but developing countries are not catching up to lower-income industrialized countries as a group. C) The growth model predicts that poor countries will catch up with rich countries, and this is what we observe across all developmental categories of countries. D) The growth model predicts that poor countries will never catch up with rich countries, but lower-income industrialized countries are catching up to higher-income industrialized countries as a group.

Assume the demand function for good X can be written as Qd = 80 - 3Px + 2Py + 10I, where Px = the price of X, Py = the price of good Y, and I = Consumer income. According to this equation:

A) a rise in the price of Y would cause the demand for X to decrease. B) X and Y are complements C) X is an inferior good. D) X and Y are substitutes.