Using the Standard Ultimate Survival Model specified in Section 4.3, and an interest rate of 5% per year effective, calculate the mean and standard deviation of the present value of a benefit of $100 000 payable (a) immediately on death, (b) at the end of the month of death, and (c) at the end of the year of death for lives aged 20, 40, 60, 80 and 100, and comment on the results. Do this in excel and show excel formulas.