per capita income

Since the question is asking for "is the per capita income GREATER", then it helps to find a LOWER bound. If we find the minimum possible per capita income, then we know all other options are above it.

We would minimize per capita income by minimizing Income and MAXIMIZING the number of people.

Since we only have lower bounds, we should use those and see what direction additional information will move us in

5,500,000,000 / 330,000 =

550,000 / 33 =

50,000 / 3 = 16,667 > 16,500. However, because population can rise above the lower limit, the per capita can decrease. By not knowing the upper bound, we don't have enough info. (E)

Thanks for the explanation.
OA is E

now I understand why do we need upper limit too to find least value..