Q."Economics is a study of mankind in the ordinary business of life" - It is the statement of :

Micro Economics studies individual economic units — a single consumer, firm, or industry — and how prices are determined in individual markets, which is why it is also called Price Theory. Macro Economics studies the economy as a whole, focusing on aggregates such as national income, the general price level and total employment, which is why it is also called Income Theory. The two branches use different methods — Micro Economics 'slices' the economy into individual unit …