Use the line graph shown. The graph shows annual cigarette consumption (in billions) for the United States for the years 1900 to 2010. Cigarette Consumption in the United States Billions of

cigarettes 700 600 500 400 300 200 100 0 1900 1920 1940 1960 1980 Year 2000 The year(s) in which 400 billion cigarettes were smoked: Estimate the year or years in which 400 billion cigarettes were smoked. If there is more than one answer, separate them with commas. DO 2010 X