Bekhorot 3: Blemishes and Their Discontents

If one sold a first-born, and had to buy it back, the question is whether that's buying it back for 10x the value of the animal specifically, or just some random large amount. Or maybe it's for 100x. Plus, the concern of blemishes -- and permanent blemishes -- in the first-born (what if it's jointly owned with a non-Jew?). Also, different kinds of blemishes could make the animal look like a pig or a goose or other kinds of mutations that aren't connected to the animal's real appearance.