In 1980 the U.S. population, broken down by regions, was $49.1$ million in the Northeast, $58.9$ million in the Midwest, $75.4$ million in the South, and $43.2$ million in the West. ${ }^{3}$ In 1990 the population was $50.8$ million in the Northeast, $59.7$ million in the Midwest, $85.4$ million in the South, and $52.8$ million in the West. Set up the population figures for each year as a row vector, and then show how to use matrix operations to find the net increase or decrease of population in each region from 1980 to 1990 .