The task is to generate the correct answer for a given math problem.

[Q]: Problem: the average weight of 4 person ' s increases by 8.5 kg when a new person comes in place of one of them weighing 95 kg . what might be the weight of the new person ?
[A]: 129 kg


[Q]: Problem: if a - b = 5 and a 2 + b 2 = 31 , find the value of ab .
[A]: 3


[Q]: Problem: how many digits are required to number a book containing 220 pages ?
[A]:
552