Our first story in the tractate! Meaning, an actual case and discussion between the sages. On how much a person pays to redeem an animal from the kohanim, whether generous or stingy — namely, via a lamb that is worth a certain amount of zuzim. What if there is no lamb? Then the redemption takes place via the value in another item. Also, in the event of depositing produce with a kuti or an ignoramus, you can pretty much continue apace when you get it back, but if you left your produce with a non-Jew, you need to treat it as produce that is new to you, as if nothing had been done, or at the very least as produce that has a doubt attached to it.