What do the authors say is the most important key to using ROI calculations that truly add value to decisionmaking? (Note: It is also the most challenging part.) Making good estimates of future benefits of an investment. Using a hurdle rate that represents the expected return of the stock market. Don't estimate what you can't prove. Question 6 After making a \$10M initial investment, you expect a \$15M return after 3 years. Use a discount rate of 8%. What is the net present value of this investment? $1.9M $2.9M $3.9M $11.9M