经济学题目,有关消费者剩余的,懂的进!

经济学题目,有关消费者剩余的,懂的进!
英文原题：
1.Hiroo is willing to pay $10 for the first widget that he purchases each year,$9 for the second,$8for the third,and so on down to $1 for the tenth and nothing for the eleventh.The market price is $3 per widget.
a) How many widgets will he buy,and what will be his consumers' surplus?
b) The price of a widget rises to $5.How many widgets will he buy now,and how will his consumers' surplus change?
c) Can you state a generalization about the relationship between the consumers' surplus obtained and the price of a commodity?
自己翻译成中文大致是这样：
Hiroo愿意花10美元购买他每年的第一部件,第二年9美元,第三年8美元,以此类推,直到价格降到第十年的1美元,第十一年为0美元.市场价格为每件3美元.
A）他将购买多少个部件?他的消费者剩余是什么?
B）若单个物品价格将涨到5美元,那么他将购买多少?他的消费者剩余又会怎么变化?
C）简述消费者剩余和一种商品的价格之间的关系.