某建筑公司A公司承包一项工程，工程总造价为8000万元，公司将2500万元的安装工程分包给B建筑公司。工程竣工之后，建设单位支付给A公司材料差价款800万元，提前竣工奖250万元。A公司又将其中的材料差价额300万元和提前竣工奖50万元支付给B公司。根据题意回答下列问题：
对材料差价和提前竣工奖的处理正确的是（）。

单项选择题The first paragraph mainly talks about （）.

A．the problems caused by river water
B．the necessity to irrigate the field
C．the water shortage in some countries
D．the canals carrying water to fields

单项选择题According to these two letters, which of the following statements is true?（）

A．Confused was glad to visit his roommate's house.
B．Confused was a little worried because he had no money for presents.
C．Confused should arrive at his roommate's house as late as possible.
D．Confused should eat the food up even if he didn't like the food.

单项选择题假如两种物品之间的交叉弹性为-3，那么，第一种物品涨价，会使： A．第二种物品的需求曲线右移 B．第二种物品的需求曲线左移 C．第二种物品的需求量沿着该物品的需求曲线下移 D．对第二种物品的需求曲线的影响不确定

单项选择题正常货是指它的： A．价格弹性大于0 B．价格弹性小于-1 C．收入弹性大于1 D．收入弹性大于0

单项选择题假如总收入TR=300Q-30Q2，Q=5，那么，价格弹性为：（）

A.0
B.-1
C.-10
D.不确定