Categorize each scenario as describing a movement along a demand curve or a shift of the demand curve.
a. College students reduce how much detergent they use for each load of laundry in response to higher detergent prices.
b. College students rush and buy discount furniture to take advantage of an unexpected price drop.
c. College students purchase many more energy drinks during finals week than during the rest of the semester.
d. Students eat out more often as the federal government increases how much grant money it provides students.