$4-$Your company is considering upgrading its computer infrastructure, and you have six options $($A$-$F$)$

available. The Minimum Acceptable Rate of Return $($MARR$)$ for this project is $12\%.$ Each computer system

has a useful life of $8$ years. Using the challenger$-$defender incremental analysis technique, determine

which option to choose and briefly explain your choice, showing your calculations.

Answer: The best option is $F.$