(5 points, 5*1) a. According to the rule of 72, how many times your money will be doubled over a 36year period if it earns a rate of return of 8% per year? Show your work. b. Using the rule of 72, estimate the value of an initial investment of $50K at the end of a 36-year period if it earns a rate of return of 8% per year? Show your work. c. According to the 4% rule, what the size of your investment portfolio needs to be in order for you to withdraw an initial annual amount of $250K? Show your work. d. Referring to part c, what will be your 4th annual withdrawal amount if the inflation rate during the 3 years since your initial withdrawal averaged 2.5% per year? Show your work.