10-31. You have been tasked with recommending one of the mutually exclusive industrial sanitation control systems summarized below. The life of both alternatives is 30 years, and residual salvage values are negligible.

Use the benefit–cost ratio method in your analysis. If the MARR is 8% per year, which answer below would you recommend? (10.9)

Alternative Gravity-fed Vacuum-led Capital investment $800,000 $1,000,000 Annual benefits less costs $106,500 $119,000

(a) Gravity-fed

(b) Vacuum-led

(c) Both systems

(d) Neither system