D Given the financial data for four mutually exclusive alternatives in the table below, determine the best alternative using a challenger defender rate of return analysis. MARR = 10%. There is also "do nothing" alternative. If interpolation is needed, please use 9% and 12% for all cases. A B . First cost $15,000 $36,000 $21.400 43,000 O &M Cost/year 1,600 400 900 1.100 Benefit/year 8,000 13,000 9,000 15,000 Salvage value 3,000 6,000 4.600 10,000 Life in years 4 O a. A O b. B , Od D