Answer: The correct answer is "2%".
Explanation: The inflation rate is calculated through the formula:
(price index 1 - price index 0 / price index 0) x 100
So : (99 - 90 / 90) x 100 = 10% is the expected inflation rate.
And the real interest rate is equal to the difference between the nominal interest rate and the inflation rate.
So: 12% - 10% = 2% is the real interest rate.