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

[Q]: Problem: a and b can together finish a work in 40 days . they worked together for 10 days and then b left . after another 15 days , a finished the remaining work . in how many days a alone can finish the job ?
[A]: 2

[Q]: Problem: a train 140 m long is running at 60 kmph . in how much time wiu it pass a platform 260 m long ?
[A]: 24 sec

[Q]: Problem: if 3 workers collect 48 kg of cotton in 4 days , how many kg of cotton will 9 workers collect in 2 days ?
[A]:
72 kg