The Navigator and others.
I think you may have missed the point. In the given answers, the units used are amps rather than amp hours.
Thus the question as quoted is bogus. It either doesn't have enough information to answer it (if you assume the answer units are as intended), or the question is correct but the answers are all wrong since the units are wrong.
I'd put good money on assuming the units had all been mistyped.
I don't think anybody is really debating the methods for calculating capacities for different cell configurations.
This sort of thing really used to annoy me when I worked as a ground instructor. You spend ages trying to fill in the gaps in students basic scientific education, one of which is that the answer is meaningless unless the units are correct, then you find this kind of thing....
CPB