Ten Principles of Economics 15
7. Candice is planning her activities for a hot summer day. She would like to go to the local swimming
pool and see the latest blockbuster movie, but because she can only get tickets to the movie for the
same time that the pool is open she can only choose one activity. This illustrates the basic principle
that
a. people respond to incentives.
b. rational people think at the margin.
c. people face tradeoffs.
d. improvements in efficiency sometimes come at the expense of equality.
8. Billie Jean has $120 to spend and wants to buy either a new amplifier for her guitar or a new mp3
player to listen to music while working out. Both the amplifier and the mp3 player cost $120, so she
can only buy one. This illustrates the basic concept that
a. trade can make everyone better off.
b. people face trade-offs.
c. rational people think at the margin.
d. decisions made at the margin are not particularly important.