instead of the service contract, rainbow engineers have devised a different option to preserve and actually enhance the capability of the machine over time. by reinvesting 20% of the annual cost savings back into new machine parts, the engineers can increase the cost savings at a 4% annual rate. for example, at the end of year one, 20% of the $5,000 cost savings ($1,000) is reinvested in the machine; the net cash flow is thus $4,000. next year, the cash flow from cost savings grows by 4% to $5,200 gross, or $4,160 net, of the 20% reinvestment. as long as the 20% reinvestment continues, the cash flows continue to grow at 4% in perpetuity. what should rainbow products do?