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10-3. A proposal has been made for improving the downtown area of a small town. The plan calls for banning vehicular traffic on the main street and turning this street into a pedestrian mall with tree plantings and other beautification features. This plan will involve actual costs of $7,500,000 and, according to its proponents, the plan will produce benefits and disbenefits to the town as follows: Benefits: Increased sales tax revenue $475,000 per year Increased real estate property taxes $300,000 per year Benefits due to decreased air pollution $80,000 per year Quality of life improvements to users_$75,000 per year Disbenefits: Increased maintenance $225,000 per year b. How does the B-C ratio change for a 20-year project life? (10.7)