If you've noticed what's special about Factor and Sum tables, you have most likely solved the problem already.
If you don't see it yet (or do see it, but are not sure what's next), it's a good idea to put yourself in the shoes of the second mother, and to try solve problem as if you were her.
So you receive the problem and "think for a while" (until you are sure that you've got all possible factor combinations and get a sum for each of them).
|Factor Table||Sum Table|
With Factor and Sum tables derived you are about to give an answer just after...