The numbers 2,4,6,9 and 12 are rearranged according to these rules；
(1) The largest isn' first, but it is in one of the first three places. (2) The smallest isn't last but it is in one of the three places.(3)The median isn't first or last numbers? What is the average of the first or last numbers? Answer:_________（要有答案和过程）