21. A company that specializes in tax shelters advertised that its special tax shelter partnerships "earn 21 percent interest for the investor each year". An independent analysis of the actual figures showed that an individual who invested S100,000 would receive a projected return of $310,000 at the end of year 10 from the investment date. What is the actual interest rate that an investor would carn from this investment, assuming annual compounding (round percentage to two decimal places)? (a) 10.83%. (b) 13.40%. (c) 11.98%. (d) 21.00%