If the demand curve for Good X shifts from Db to Da then Sma

If the demand curve for Good X shifts from Db to Da, then SmallCircle firms would be willing to supply more of Good X than before at each possible price. SmallCircle people\'s incomes must have increased SmallCircle people are willing to buy less of Good X than before at each possible price SmallCircle the price of Good X has increased.

Solution

The shift is due to the increase in the incomes of the consumer because people are willing to buy more of a good at each possible price.