完形填空。

    A shop owner closed his shop and went home. He was very 1  but just as he went to bed the telephone 2  . A man asked, "What time do you open your shop?"The shop owner was 3  about this phone call. He put down the receiver without answering and went  4 to bed. A few minutes   5  the telephone rang  6  and the man asked the  7  question. The shop owner became very   8   and he shouted, "You needn't ask me when I open the shop because l won’t let you  9. ""Oh, no. I don’t want to   10  in, "the mail said, "l want to go out. "

如图，已知菱形ABCD的对角线AC、BD的长分别为6cm、8cm，AE⊥BC于点E，则AE的长是____ ．