There is copper 4 tiles away from our cultural border to the NW. And there is copper 6 tiles away from our borders to the SE beyond the marble. So that is best how to use the slavery option. Already I'm starting to learn this game better. Thank you. Next player may want to take retro V's advisement and have the worker stop chopping the forest. At least it will only take 2 more turns to finish that chop in the future.