The population of the United States from 1970 to 2010 can be modeled by a function where is the population (in millions) and is the time in decades since 1970. Some values for this function are shown in the table. (Note: represents 1970.) 0 1 2 3 4 203 227 249 281 309 What was the average rate of change, in millions of people per decade, in the U. S. population from 1970 to 2000? Round to the nearest whole number.