From this I inferred that engine 2 had a carburetor problem. In this article, I discuss the specific engine/carburetor problem, and the surprising solution to this problem.

Now it was time for the nerve-wracking part of the job: actually removing anything from the hanging wall we deemed to be in need of removal because it was either loose, could be loose, looked loose, or we felt it was just downright dangerous

When detecting an area that has been cleaned to bedrock and you have new trees growing, always make sure you get your coil as close as possible to the tree. Why?

For simplicity, I will assume that you wish to make enough profit so that you can comfortably pay your bills using just the profits from the mine.