BANKING of The Mystery

When economics students read textbooks, they learn, in
the "micro" sections, how prices of specific goods are
determined by supply and demand. But when they get
to the "macro" chapters, lo and behold! supply and demand built
on individual persons and their choices disappear, and they hear
instead of such mysterious and ill-defined concepts as velocity of
circulation, total transactions, and gross national product. Where
are the supply-and-demand concepts when it comes to overall
prices?