Display DIV when javascript/jquery condition is met (jsFiddle link included)

When the ‘rest’ time countdown clock reaches 10, I want the “rest” div to
show and display over the “display” div, causing the “display” div to be covered.
When the rest time reaches 5, I want the “rest” div to hide, making the “display” div
reappear.

http://jsfiddle.net/n2learning/9FPG8/2/

Any help would be great,
DK