Challenge question. In the chapter text, we dealt exclusively with a single lump sum, but often we may be looking at several lump-sum values simultaneously. Let's consider the retirement plan of a couple. Currently, the couple has four different investments: a 401(k) plan, two pension plans, and a personal portfolio. The couple is 7 years away from retirement. They believe they have sufficient money in their plans today so that they do not have to contribute to the plans over the next 7 years and will still meet their $2 million retirement goal. Here are the current values and growth rates of their plans: 401(k): $92,000 growing at 6.5%. Pension Plan One: $256,000 growing at 8%. Pension Plan Two: $202,000 growing at 7.75%. Personal Portfolio: $120,000 growing at 8.5%. Does the couple have enough already invested to make their goal in 7 years? Hint: View each payment as a separate problem, and find the future value of each lump sum 7 years from now. Then add up all the future values