[Number5]

If batters reached on an error, you would try to guess how many runs would have scored if those errors would have been outs instead.

So if your defense bottles and lets say the first 3 batters reach on errors, you will never give an earned run no matter how many runs you will give up this inning, because the inning should have been over after those 3 batters. Anything else isn't "earned" against the pitcher, but only scored because errors made the inning continue longer than "earned".

Let's say the inning goes reached on error, hit, 3 run shot, reached on error, RBI triple , RBI groundout, strikeout, strikeout.

So 5 runs score, how many are earned?

The first isnt earned, because the batter should have been out.
The 2nd and 3rd would have still happened without an error, so those are earned.
The 4th batter also reached on an error, so unearned.
The 5th guy reached on a triple and scored on a groundout. Those should been earned. However, the last groundout would have ended the inning, so also unearned.

5 runs, 2 earned.