"I don't want to spend more than twenty dollars for a backpack." Consumer spending is seventy percent of the economic activity in the United States.

VOA: special.2009.08.21

So we put one item in the backpack 9 and we've got a value of 9.

所以我们在背包里放一件物品,而它的价值是。

麻省理工公开课 - 计算机科学及编程导论课程节选