用A、B、C、D、E、F六种燃料去染下图的两个调色盘，要求每个调色盘里的六种颜色不能相同，且相邻四种颜色在两个调色盘里不能重复，那么共有　____ 种不同的染色方案（旋转算不同方法）．

Children go back to school in_______.

阅读下文，回答问题
                                                                                                  On the beach
    It is a fine day. A lot of people go to the beach to enjoy sunshine. Some people are swimming like fishes in the sea. On the beach，some young people are playing volleyball.
    Some of them are lying under the coconut trees. And some old people are chatting with each other. What are the children doing? Look! They are making castles with spade and sand. They are having fun。
⑴⑵⑶⑷⑸根据短文内容，判断正误；⑹根据短文内容填空。

若不等式ax²+bx+c≤0的解集为{x|x≤1或x≥2}，则点P（b，c）的轨迹是（   ）

已知A、B分别在射线CM、CN（不含端点C）上运动，∠MCN= $\frac{2}{3}$ π，在△ABC中，角A、B、C所对的边分别是a、b、c．

（Ⅰ）若a、b、c依次成等差数列，且公差为2．求c的值；

（Ⅱ）若c= $\sqrt{3}$ ，∠ABC=θ，试用θ表示△ABC的周长，并求周长的最大值．