Hill Climb Categories Average Gradients?

I know that there are hill climing categories of Cat 4 to Cat 1 and SC special category i was just wanding what the average gradient and maximum distance they would do for each category any one know?
;D ??? ???
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Surf to
http://www.cyclingnews.com/results/2000/jul00/tdfrance00/tdfrance00map.shtml

This map shows the distance of the climbs and their gradient it also show what category the climb is.

cheers!