Task: Question Answering
Input (English): Question: A can do a piece of work in 20 days. B in 15 days A and C in 12 days. In how many days can A finish the work if he is assisted by B on one day and C on the next, alternately?

 Option A: 2 days

 Option B: 5 days

 Option C: 8 days

 Option D: 7 days

 Option E: 9 days
Output (English): Option C