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

[EX Q]: Problem: the least number which should be added to 1789 so that the sum is exactly divisible by 5 , 6 , 4 and 3 is ?
[EX A]: 11

[EX Q]: Problem: the sum of all the digits of the integers from 18 to 21 inclusive is 24 ( 1 + 8 + 1 + 9 + 2 + 0 + 2 + 1 = 24 ) . what is the sum t of all the digits of the integers from 0 to 99 inclusive ?
[EX A]: 900

[EX Q]: Problem: a tank is filled by 3 pipes a , b , c in 6 hours . pipe c is twice as fast as b and b is twice as fast as a . how much will pipe a alone take to fill the tank ?
[EX A]:
42 hr