请教一道经济学题，关于social surplus。。

Question

Consider the following monthly rice demand and supply equations for a market:
Qd = 20 – P
Qs = –10 + 2P,
where P is the price of rice per kg and the quantities are measure in thousand kg. This
rice market is perfectly competitive.

(a) What are the equilibrium price and quantity in this market?
my answer: 10 10
The local government plans to assist the rice producers by increasing the price of rice.
It is studying the following two alternative schemes as a means of increasing price.
In the first scheme, the government offers to purchase, at a price of $15 per kg, any
amount of rice that is produced but not sold to consumers. The government then
destroys all the rice purchased.
(b) Under the first scheme, what is the amount of rice purchased by the government?
my answer: 15
(c) Under the first scheme, what is the social surplus at market equilibrium?
my answer: 112.5

In the second scheme, the government decides to purchase, at a price of $15 per kg,
all the rice produced. That is, the rice producers will only sell their rice to the
government at a price of $15 per kg. The government then puts all of the rice
purchased on the market for resale to consumers at whatever price consumers are
willing to pay for that quantity.
(d) Under the second scheme, what price will the government receive when it resells
all of its rice?
my answer: 0 (??? really?? )
(e) What is the social surplus associated with the second scheme?
my answer: 300

(f) Which scheme will you recommend to this government? Briefly explain your
answer.
这个怎么讨论啊

多谢各位。刚刚学经济学。很多东西搞不清。

Answer 1

b),问的是amount,不是quantity
d), 我也觉得是0
e)，生产者剩余是300，消费者免费有，也有剩余是200，所以社会剩余是300+200=500
f) first scheme, producer surplus is 100 while social benifit is -112.5( social benifit=social surplus-cost of government)
second scheme, porducer surplus is 300 while social benift is 200
So recommend the second scheme.

Answer 2

楼上的三个理由分别代表三个总供给模型，楼主不妨参考下曼昆的宏观经济学第十三章。