A machine with an initial purchase price of $18000 has a useful life of 10 years. The usage of this machine is forecasted to bring us $7000 a year in savings. At an interest rate of 1% how many years will it take to payback the investment? 1-2 years 2-3 years 3-4 years 4-5 years 56 years 6-7 years 7-8 years More than 8 years