Task: Question Answering
Input (English): Question: On a certain date, Pat invested $7,000 at x percent annual interest, compounded annually. If the total value of the investment plus interest at the end of 10 years will be $28,000, in how many years total will the total value of the investment plus interest increase to $56,000?

 Option A: 15

 Option B: 16

 Option C: 18

 Option D: 20

 Option E: 24
Output (English): Option A