On Rashi, in the commentary beginning "Even though they accepted it together initially and he said to him..." Rashi's intent is that they initially accepted it together in a general way (stam), and afterwards, one said to the other, etc. This interpretation resolves the matter.

On Tosafot, in the commentary beginning "Come and hear: If they stipulated..." The question is raised: Why not derive the rule from the earlier clause (reisha)? Tosafot respond that this is because the Gemara wants to clarify, etc. Their explanation is as follows: From the earlier clause, one could infer that in a general case (stam), the ruling is lenient, as it says, "He should not say, etc."—implying that in a general case where nothing was explicitly stated, it would be permitted. To address this, Tosafot explain that one cannot derive leniency from the earlier clause (reisha), because it is possible that the phrase "He should not say, etc." is only mentioned due to the subsequent clause (seifa), "If they stipulated, etc." This teaches that even if one explicitly stipulates, "You take Shabbat in exchange for weekday," it is permitted. Without the earlier clause, we might have assumed the permission only applies when one does not explicitly stipulate "Take Shabbat in exchange for weekday," but rather says initially, "Take days in exchange for days," and includes Shabbat as part of the gentile's portion implicitly. Thus, there is no difficulty in asking, "What is being inferred? If they stipulated, it is permitted—implying that in a general case, it is prohibited?" Since one could respond that the phrase "If they stipulated" even permits an explicit stipulation, the Mishnah should have included the general case of permission (stam) to teach the more significant novelty (chidush) that a general case is permitted, all the more so if there was an explicit stipulation. As Tosafot write later, "Certainly, if they stipulated, it is permitted, even if they explicitly calculate." The novelty of a general case being permitted is greater than the novelty of a stipulated case in all circumstances. This explanation resolves the issue.

On Tosafot, in the commentary beginning "We do not place an animal, etc." Tosafot write, "This reasoning does not stand, etc. And in two tractates, everyone agrees there is no order." This is difficult to understand: Why is it necessary to mention that "everyone agrees there is no order"? Even if there were an order, the case here involves an anonymous Mishnah (stam) followed by a dispute. The anonymous ruling is here in Seder Nezikin in Tractate Avodah Zarah, and the dispute appears later in Seder Taharot in Tractate Parah. Investigate this carefully.