How to append child

[admin]

Hello,
i am trying to append the childe with somedata

my script i slike below

<Managed id="1">
<Traffic id="1" name ="t1" des ="des1">
<annotation>Traffic 1 </annotation>
</Taffic>
<Traffic id="2" name ="t2" des ="des2">
<annotation>Traffic 2 </annotation>
</Taffic>

<Traffic id="3" name ="t3" des ="des3">
<annotation>Traffic 3 </annotation>
</Taffic>
</Managed>

Now I Would like to append the Fourth child as below

my fourth child should be like this
<Traffic id="4" name ="t4" des ="des4">
<annotation>Traffic 4 </annotation>
</Taffic>

Can anybody send me the script for to how to append the childe which contains other attribute also

Thanks