An asset purchased 3 years ago for $30,000 is harder to maintain than expected. It can be sold now for $10,000 or kept for a maximum of 3 more years. in which case its operating cost will be $5,000 each year, with a salvage value of $8,000 after 1 year, $6,000 after two years and $4,000 after three years. A suitable challenger will have an annual worth of $-20,000 per year. At an interest rate of 10% per year, should the defender be replaced now, one year from now, or two years from now