12. (This problem is challenging.) The economy of Elmendyn contains 2,000 $1 bills.

a. If people hold all money as currency, what is the quantity of money?

b. If people hold all money as demand deposits and banks maintain 100 percent reserves, what is the quantity of money?

c. If people hold equal amounts of currency and demand deposits and banks maintain 100 percent reserves, what is the quantity of money?

d. If people hold all money as demand deposits and banks maintain a reserve ratio of 10 percent, what is the quantity of money?

e. If people hold equal amounts of currency and demand deposits and banks maintain a reserve ratio of 10 percent, what is the quantity of money?