it's taken from manhattan archive- which includes some of the hardest i have seen and frankly i believe that only som GC legends will be able to solve some of them under 4 minutes.
by the way, how do you decide to prefer E (which is correct) and not C
Vow, MGMAT? i guess than must be to trick people.
Basically, if you combine A and B, there is no additional info other than what we have achieved in B. Because remember that A doesn't provide any other info other than its just different way of expressng N!.