Answer: None of the above
Step-by-step explanation: Set up a few sample calculations to see that neither option will result in a correct calculation.
a b I a-b I IaI-IbI IaI+IbI
1 5 4 -4 6
5 1 4 4 5
1 -5 6 -4 6
With just these three random a and b points, we can see that Ia-bI values occassionally do not match the other two options. None of the above.
