Task: Question Answering
Input (English): Question: The banker's discount on $1600 at 15% per annum is the same as true discount on $1680 for the same time and at the same rate. The time is:

 Option A: 2 months

 Option B: 1 months

 Option C: 4 months

 Option D: 8 months

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