You are considering upgrading some manufacturing facilities by purchasing one of three different machines, each with the same production capacity. Machine A costs $30,000, has a life of 40 years, annual maintenance costs of $1500, and a salvage value of $5000. Machine B costs $20,000, has a life of 20 years, annual maintenance of $2000, and salvage value of $3000. Machine C costs $10,000, has a life of 10 years, annual maintenance of $4000, and no salvage value. Determine the most economical choice based on minimizing the present value of total costs. Use an annual discount rate of 10%. Assume that initial costs, annual maintenance, and discount rates are constant throughout the analysis period.