Task: Question Answering
Input (English): Question: Machines X and Y produce bottles at their respective constant rates. Machine X produces k bottles in 6 hours and machine Y produces k bottles in 12 hours. How many hours does it take machines X and Y , working simultaneously , to produce 12k bottles?

 Option A:  8

 Option B:  12

 Option C:  15

 Option D:  48

 Option E:  24
Output (English): Option D