Dixon Shuttleworth has a large sum of money that he wants to invest to finance his retirement. He has been presented with three options. The first investment offers a 5% return for the first five years, a 10% return for the next five years, and a 20% return thereafter. The second investment offers 10% for the first ten years and 15% thereafter. The third investment offers a constant 12% rate of return. Determine which of these investments is the best for Dixon if he plans to retire in the following number of years. A. Fifteen years B. Twenty years C. Thirty years