Thank you very much for helping!

An asset purchased 2 tears ago for $40,000 is harder to maintain than expected. it can be sold now for $12,000 or kept for a maximum of 2 more years, in which case its operating cost will be $20,000 each year, with a salvage value of $10,000 after 1 year or $9000 after two years. A suitable challenger will have an annual workh of $-24,000 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