(Mishnah): If the dough became Dimu'a (mixed with Terumah) before she kneaded it, it is exempt, for Meduma is exempt. [If it became Dimu'a] after she kneaded it, it is obligated.

If a Safek Tum'ah arose before she kneaded it, it [may be] done b'Tum'ah. [If the Safek arose] after she kneaded it, it must be done b'Taharah.

(Gemara - R. Yonah) Question: R. Chiyah Ruba taught two laws, and one argues with the other!

Tevel, its count is like that of Chulin (it can become a Rishon or Sheni l'Tum'ah, but not a Shelishi).

Any Safek that disqualifies Terumah, it disqualifies Chulin from becoming Terumah.

Question: If Tevel's count is like that of Chulin, why does it disqualify Chulin from becoming Terumah? Its count is like Chulin!

Remark (R. Yosi): We learned both of these in Mishnayos! (Your question is not against R. Chiya, rather, against the Mishnayos!)

Tevel's count is like Chulin - a Mishnah teaches, if a food of Ma'aser was Huchshar through a liquid, and a Tevul Yom or Tamei hands touched it, [even so] one may separate from it Terumas Ma'aser b'Taharah, for it is a Shelishi (and a Shelishi of Tevel is Tahor).

Inference: Tevel's count is like Chulin.

Any Safek that disqualifies Terumah, it disqualifies Chulin from becoming Terumah - our Mishnah teaches, if a Safek Tum'ah arose before she kneaded it, it [may be] done b'Tum'ah; after she kneaded it, it must be done b'Taharah.

(Rav Sheshes): [Our Mishnah] is like R. Akiva, for R. Akiva says that [if one cannot separate Chalah b'Taharah], he makes [his dough] b'Tum'ah, and does not make it Kavin.

(R. Ze'ira): It is like everyone. ['it is done b'Tum'ah' means that] he makes it Kavin b'Tum'ah. (SHA'AREI TORAS ERETZ YISRAEL)

Question (R. Chiyah bei R. Bun, to R. Ze'ira): It was taught [in a Tosefta like our Mishnah, and it says] also with other species (if there was a Safek Tum'ah before final processing, he may do [and tithe] them b'Tum'ah; after final processing, they must be done b'Taharah). Can you say that he makes it Kavin due to the Safek?! (This does not exempt from Terumah and Ma'aseros!)

Rav Zavida: Also I would challenge [R. Ze'ira from this Tosefta].

(R. Yosi citing R. Heila): According to Torah law, one may be Metamei his Tevel, for it says "va'Ani Hinei Nasati Lecha Es Mishmeres Terumosai'' - Terumah must be guarded (even if it is Tamei, you may not be Metamei it more), but [Tamei] Tevel need not be guarded;

However, since it says "u'Nesatem Mimenu Es Terumas Hash-m l'Aharon ha'Kohen'' - do [it in Taharah] so it will be given to Aharon ha'Kohen in his Kehunah (so he can eat it; if the Tevel is Tahor, separate Terumah b'Taharah. We explained this like RITVA, Gitin 61a.)

Here (Tevel that is Safek Tamei), since you cannot give [the Terumah or Chalah] to the Kohen in his Kehunah, you may be Metamei it.