(b) The owner of an office building has $100,000 to invest. Which one of these alternatives should be adopted? Her MARR is 5%. Renovation: If this sum was used to renovate the building, it is estimated that the building value will be $672,750 more in 20-years' time when it is sold. Windows: If the sum is used to upgrade windows, the annual savings in heating costs will be $12.558