4. Use the concept of opportunity cost to explain the following.

a. More people choose to get graduate degrees when the job market is poor.

b. More people choose to do their own home repairs when the economy is slow and hourly wages are down.

c. There are more parks in suburban than in urban areas.

d. Convenience stores, which have higher prices than supermarkets, cater to busy people.

e. Fewer students enroll in classes that meet before 10:00 A.M.