Task: Question Answering
Input (English): Question: X can do a piece of work in 15 days. If he is joined by Y who is 50% more efficient, in what time will X and Y together finish the work?

 Option A: 10 days

 Option B: 6 days

 Option C: 18 days

 Option D: Data insufficient

 Option E: None of these
Output (English): Option B