The above sentence appeared in a section describing the use of 其 (기) as a disjunctive "or," which means the "or not?" phrase would be a separate sentence from the first option. I wonder, however, how the possessive pronoun "其 (기)" came to mean or imply "or."子以秦爲將救韓乎? 其不乎?“Do you think that Qín will save Hán or not?”
In the "Du's Handbook" translation, 以 (이) and 爲 (위) seem to have been translated together as "to think," but by paraphrasing it like that, I think a fairly important detail of the sentence is lost. Here is my more literal translation:
In my translation, the "see" really means "to think," but I used "see" so that I could translate 爲 (위) as "as." I could have translated 爲 as "is," but I used "as" so that I could later translate 其 (기) as the possessive pronoun it is. A possessive noun or pronoun is followed by a noun or noun phrase. The 其 here does not necessarily mean "or," but by its being a possessive pronoun, it implies that an "or as" should precede it when translating it in English.子以秦爲將救韓乎? 其不乎?[Do] you (子) see (以) Qín (秦) as (爲) going to (將) to save (救) Han (韓乎)? [Or as] their (其) not (不) [going to] (不乎)?
I have written this post only to try to explain how the possessive pronoun 其 (기) came to mean "or" when it is used in the way it was used here. In reality, I will also be translating 其不乎 (기불호) as "or not?"