Suppose that an economist hypothesizes that the annual quantity demanded of a specific computer brand (QD) is determined by the price of the computer (P) and the average income of consumers (Y) according to QD = Y - 3P.

Assuming Y = $6,000, calculate the change in the quantity demanded when the price increases from $1,000 to 2,000. Do the same for a price increase from $500 to $1,000 and from $500 to $2,000. Call the change in the quantity demanded and the change in the price . ( means "change in.")