已知△ABC的内角A，B，C所对应的边分别为a，b，c，且面积为6，周长为12，cosB= $\frac{3}{5}$ ，则边b为（   ）

某市政府为了引导居民合理用水，决定全面实施阶梯水价，阶梯水价原则上以住宅（一套住宅为一户）的月用水量为基准定价：若用水量不超过12吨时，按4元/吨计算水费；若用水量超过12吨且不超过14吨时，超过12吨部分按6.60元/吨计算水费；若用水量超过14吨时，超过14吨部分按7.80元/吨计算水费．为了了解全市居民月用水量的分布情况，通过抽样，获得了100户居民的月用水量（单位：吨），将数据按照0，2，（2，4，…，（14，16分成8组，制成了如图1所示的频率分布直方图．

（Ⅰ）假设用抽到的100户居民月用水量作为样本估计全市的居民用水情况．

（ i）现从全市居民中依次随机抽取5户，求这5户居民恰好3户居民的月用水用量都超过12吨的概率；

（ⅱ）试估计全市居民用水价格的期望（精确到0.01）；

（Ⅱ）如图2是该市居民李某2016年1～6月份的月用水费y（元）与月份x的散点图，其拟合的线性回归方程是 $\widehat{y}=2x+33$ ．若李某2016年1～7月份水费总支出为294.6元，试估计李某7月份的用水吨数．

―Karen, can I talk to you for a minute?
―Sure, ________?

完形填空

    According to a Chinese saying, he who doesn't reach the Great Wall of China is never a great man.

    Growing up in Beijing I1 its historical sites and natural attractions perfectly well. However, I'd 2 climbed the Great Wall before until recently. I, along with my friends3for the top. We soon discovered that the hike was much more 4 than we had imagined. But we didn't 5.It took us about two hours to finally6 where we had wanted to get to.

    As I 7 at the top of the Great Wall, I looked back at the waves of8 walking to the top. At that moment, I saw an amazing 9 that would forever change my opinion on humans' limits. I saw young couples carrying their children, walking10 but surely towards the top. They would stop once in a while to take a11 under the hot sun.

    As I stood there, I began to 12 words that can describe us humans. If one would like to describe Giraffes (长颈鹿), he/she would use words such as 13 and long-necked -But what about us? I took another look down below and my 14began to gather, persevering (坚持不懈的), determined, and 15As these words came into my mind, I 16 that it was not appearance or physical characteristics that should define (定义) us humans, but the 17 that we share.

    I don't know if I became a 18 man after returning from this 19 according to the Chinese saying20 I surely returned as a more thoughtful person.

面积最大的热带沙漠气候分布区是在（　　）