Your friend would like your assistance in determining how much to save for retirement. He is planning to invest $ 10,000 in a tax- sheltered retirement fund at the end of each year (i.e., appreciation of the fund is not taxed). The rate of return each year can be modeled as a normally distributed random variable with a mean of 12 percent and a standard deviation of 2 percent, and can vary from year to year. He is 45 years old now. a) In the base case, assuming the rate of return is deterministic at 12 percent each year, how much money should he expect to have in his retirement fund at the end of age 60 (including the investment made at the end of that year)? (5) (Note: Please calculate the entire cash flow over the years and do not use any existing financial function in Excel to calculate the answer, so that you can incorporate uncertain return rates in each year in the following parts)