An injection mold machine has an initial cost of $25,000 and can be sold at any time during its first 4 years of service for $10,000. The salvage value of the machine decreases by $2,000 every year after that. The maintenance costs for this machine are projected to be $6,500 for the first year and will increase by 9% every year. If the interest rate is 14%, what is the economic life for this machine?