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A common standard of significant change is 10%. A project's first cost is $20,000, the expected life is 15 years, and the interest rate is 8%. How large must the salvage value be so that its PW is 10% of the first cost? If the salvage value is $4,000, how short must the life be so that the salvage value's PW is 10% of the first cost? If the salvage value is $4,000, how low must the interest rate be so that the salvage value's PW is 10% of the first cost