Explain whether each of the following events represents a shift in the demand curve or a movement along the demand curve. Draw your answer.

a. A store owner finds that customers are willing to pay more for umbrellas on rainy days.

b. When XYZ Telecom, a long distance provider, offered reduced rates on weekends, the volume of weekend calling increased sharply.

c. People buy more long stem roses the week of Valentine’s Day, even though the prices are higher than at other times during the year.

d. The sharp rise in the price of gasoline leads many consumers to join car pools in order to reduce their gasoline purchases.