The expected average rate of return for a proposed investment of $6,720,000 in a fixed asset, using straight-line depreciation, a useful life of 20 years, no residual value, and an expected total income of $20,160,000 over the 20 years, is (round to two decimal places)

a. 1.50%

b. 30.00%

c. 60.00%

d. 15.00%