According to the 2018 Diary of Consumer Payment Choice, a study conducted by the Federal Reserve’s Cash Product Office, on a typical day the average consumer 18 years of age and older held about $59 in currency. As noted in the chapter, there is actually about $5,000 of currency in circulation for every person (adult and child) in the United States. 

a. How can the amount of U.S. currency in circulation be so much larger than the amount held by the U.S. population? 

b. What does the difference in part (a) imply about the measures of the money supply of the United States?