Havoc 12. I remember the number but not the name (something about timing or something), and you get 12 builders.
I'll edit in my question when I think of it.
EDIT: Ok, here goes.
Refering back to that same Taxing set of what I presume is Amiga Lemmings, name the only level of this set whose minimum release rate is exactly equal to the sum of all tasks assigned to you to solve the level.