Read and order仔细读句子，根据提示，排列对话吧！

   1  What colour do you want?

   2  Here you are.

   3  Twenty yuan.

   4   How much are they?

   5   Can I help you?

   6   That's fine. I'll take them.

   7   I want to buy two pens.

   8     A blue one and a black one.