4. The nominal salary paid to the president of the United States along with data for the consumer price index (CPI) are given for various years below. Year Presidential salary CPI (2000=100) 1920 $ 75,000 11.6 1940 75,000 8.1 1960 100,000 17.2 1980 200,000 47.9 2000 400.000 100.0 Calculate the president's real salary measured in the purchasing power of the dollar in 2000 b In which year was the real presidential salary the highest? The lowest? If the president's nominal salary was constant between 1920 and 1940, what happened to the real salary? Can you explain why