If people hold all money as currency, the quantity of money is $900 . If people hold all money as demand deposits and banks maintain 100 percent reserves, the quantity of money is $900 . If people hold equal amounts of currency and demand deposits and banks maintain 100 percent reserves, the quantity of money is $900 . If people hold all money as demand deposits and banks maintain a reserve ratio of 12.5 percent, the quantity of money is $ . If people hold equal amounts of currency and demand deposits and banks maintain a reserve ratio of 12.5 percent, the quantity of money is $ .