This should go under the standard necron section not the "Army lists"
And you can't have 4 squads of 5, they're a fast attack choice and some jerk decided necrons don't get more then everyone else. I'd say 2 squads of 10 anyways, scarabs are something i generally use as a speed-bump BUT they are pretty nasty in large numbers (that's 30 wounds and 40 attacks on a charge, not something to be scoffed at)
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