In a replacement analysis for a vacuum seal on a spacecraft, the following data are known about the challenger: the initial investment is $11,000; there is no annual maintenance cost for the first three years, however, it will be $1,000 in each of years four and five, and then $4,000 in the sixth year and increasing by $1,000 each year thereafter. The market value at the end of year k is 50% of year k-1 at all times, and MARR is 5% per year.

What is the economic service life (ESL) of this challenger?

What is the EUAC corresponding to the economic life in part a?