21. Planing for retirement. You anticipate an average income of $10,000 per month over your working life. With this in mind, you begin planning for retirement. For this exercise, assume an APR of 5% and round all answers to the nearest whole dollar. a. Taking into account income from Social Security, you think you will need a monthly income of about 75% of your working income. That is you want to provide a monthly retirement income of $7500 for 20 years. Use the annuity yield goal formula (Formula 4.11) to determine the size of the nest egg needed for retirement. b. Use the deposit needed formula (Formula 4.9) to determine the monthly deposit required to meet the goal from part a. Assume a working life of 45 years. 11