Bekhorot 21: Making Assumptions about Animals' Prior Offspring

More on the female triplet goats who each have triplets to lead into a discussion of Rabbi Shimon's position, as compared to the tanna kama. Specifically about whether a goat that has miscarried will delay for a spate of time before mating again. Which in turn gets into how to count that time, even to the final day. Also, a dispute between Rav and Shmuel (and Rabbi Yochanan) as to whether one can take it as a given that an animal purchased from a non-Jew has had progeny before. How much should one expect the seller to share about the animal he's selling? How much should the buyer be expected to ask?