4. I am planning for my retirement, and at the beginning of this year and each of the next 39 years, Im going to contribute some money to my retirement fund. Each year, I plan to increase my retirement contribution by $500. When I retire in 40 years, I plan to withdraw (at the beginning of each year) $100,000 per year for 20 years. Ive made the following assumptions about the yields for my retirement investment portfolio: During the first 20 years of my investing, the investments will earn 10 percent per year. During all other years, my investments will earn 5 percent per year. Ive assumed that all contributions and withdrawals occur at the beginning of the year. Given these assumptions, determine the least amount of money I can contribute this year and still have enough to make my retirement withdrawals? [10 marks] 5. Using the excel workbook provided under Q5 worksheet: i. Determine the commission due to the Sales rep without the use of a choose function [5 marks] ii. Determine the commission due to the Sales rep with the use of a choose function