6. You have two options for additional guaranteed monthly payments in retirement (annuities). Go to the Annuities worksheet to calculate the value of each of these options. a. The first annuity costs $20,000 and pays you $200 per month for 120 months (10 years). In cell B5, enter a formula to calculate the present value of this investment. Remember to express the Pm argument as a negative number and set the Type argument to 1 as the payment will be made at the beginning of each month. (Hint: Use the PV function.) b. The second annuity also costs $20,000 but it pays a variable annual payment. In cell B13, enter a formula to calculate the present value of this investment using the annual interest rate in cell B8 and the payment schedule in cells B14:B23. (Hint: Use the NPV function.)