Suppose that Paul the pitcher begins an inning by striking out Adam, and then he walks Billy. The next batter is Charlie, who hits a foul ball that the first baseman drops. Subsequently, he is charged with an error on the play. Charlie proceeds to hit a home run. Paul concludes the inning by striking out David and Ed.
How does this inning get scored in terms of earned v. unearned runs? Clearly, Charlie's run is unearned because of the error. But what about Billy's run?
I would assume that there are 3 options available for the official scorer:
1) Ignore the end result of Charlie's at bat (the homer, which implies Billy's run is unearned).
2) Assume that the next hitter (David) would have the same end result as Charlie (i.e., David would hit a homer, which implies Billy's run is earned).
3) Which ever approach is more favourable for the pitcher.
How would the answer change if instead of David and Ed striking out, David hit a triple (which would have scored Billy had the foul ball been caught), and then Ed and Fred strikeout? My guess is that the scorer would take approach 1, assume Charlie was actually out, and proceed from there.