Given:
Initial Investment = 109,296
annual return = 12,000 for 15 years.
Usually the expected rate of return uses rates in percentage form. ERR is calculated by taking the average of the probability distribution of all possible returns.
However, based on the given figures, I think the best formula for this would be the accounting rate of return.
ARR = Average Accounting Profit / Average Investment
ARR = 12,000 / 109,296
ARR = 0.10979
ARR = 0.10979 100% = 10.979 or 10.98%
The expected rate of return is 10.98%