Problem $6\mathrm{.}9$: Bob has done an okay job planning for his future, but he knows retirement is not that far off and he needs to update his financial plans. Bob plans to retire in $15$ years and currently has $$100,000$ in a savings account and $$300,000$ in a stock fund. In addition, he plans to invest $$8,000$ per year into his stock fund at the end of each of the next $5$ years, and then up the amount to $$10,000$ per year at the end of the final $10$ years until he retires.

a$.$ Assuming Bob's savings account returns $4\%$ compounded annually, and his stock fund will return $9\%$ compounded annually, how much will Bob have at the end of $15$ years?

b$.$ If Bob expects to live for $25$ years after he retires, and at retirement he deposits all of his savings and stock investments in a bank account paying $5\%,$ how much can he withdrawal each year after he retires $($making $25$ equal withdrawals beginning one year after he retires$)$ so that Bob ends up with a zero balance at death?

Note: there are multiple methods that can be used to solve this problem. The template below is laid out for one of those methods, but you can chose another.

Use excel formulas for each question