Crown of the Empire (UP)

You can knock this out by level 10 if you upgrade the workers in each level as you go. You don’t have to do it that way. You can just pick and choose when you want to upgrade them. You could also repeat a level if you wanted it earlier.

Level 4 adds 1 worker
Level 5 adds 1 worker
Level 6 adds 2 workers
Level 8 adds 2 workers
Level 9 adds 2 workers
Level 10 adds 2 workers