Bullie Jean has $1.20 to spend and wants to buy cither 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-ofts.
c. rational people think at the margin.
d. decisions made at the margin are not particularly important .

b. people face trade-offs

Explanation:

From the question, we are informed that Bullie Jean has $120 to spend and wants to buy cither a new amplifier for her guitar or a new mp3 player to listen to music while working out.

We are further informed that the amplifier and the mp3 player cost $120, each and so she can only buy one. This shows that people face trade offs and have to make a choice regarding some decisions. Here, an opportunity cost will be the one that she didn't buy at the expense of the other.

answer; ///(c) the way a government controls the supply,availability,and value of money;