The small town of Middling experiences a sudden doubling of the birth rate. After three years, the birth rate returns to normal.
a. The market for an hour of babysitting services in Middling today
b. The market for an hour of babysitting services 14 years into the future, after the birth rate has returned to normal, by which time children born today are old enough to work as babysitters
c. The market for an hour of babysitting services 30 years into the future, when children born today are likely to be having children of their own.