Mason asks: "Please define the ‘real-bills doctrine."

When a firm seeks credit, it writes bills of 
exchange. They expire in 90 days, at which time 
the bills can be redeemed for cash.  A firm can 
pay its suppliers with these bills, discounted, 
or it can present them to a bank, discounted, in 
exchange for cash in its demand deposit, used to 
pay labor. These real bills provide a flexible 
supply of money substitutes or credits for the needs of trade.

Fred Foldvary