Chapter 8! And a new mishnah. On mixtures, when something that is prohibited for benefit is mixed with "regular" items (or, in these cases, animals) of the same kind - such that that which is prohibited for benefit cannot be identified, then the whole lot would need to be put to death. Or, depending on the nature of the prohibition, perhaps all animals put out to pasture until they got a blemish, rather than put to death. Those animals were then sold, and the money was used to purchase new offerings. Also, the details that "any amount" of that which is prohibited for benefit is startling in the larger amount that might be destroyed for that small amount. Note the parallel mishnah in Tractate Temurah, and the fact that both mishnayot (here and there) are needed to teach these laws, or we might end up drawing the wrong conclusions.