Answer:
a/ 20 days per year on average
b/ The use of road salt to is an effective deicer method. However, it will eventually causes some harmful impact on the environment including but not limited to increasing in water/soild salinity, contamination of public drinking waters, destroy the soild structure and slowly killing of trees and plants. Luckily, there are some other options which are more environment-friendly such as Cheese brine, Sand, Urea, Beet molasses
Explanation:
a/ To evaluate the investment of the new snowplow, denote X is the average amount of saving per a year as the new snowplow is used.
Consider the average amount of saving as an annuity for the next 12 years, with the discount rate of 14%. The present value (PV) = 45,000 - 2,500/1.14^(-12) =$44,481.1
Thus, to obtain the rate of return of 14%, PV of the annuity should be equals to $44,481.1 meaning: 44,481.1= (X/14%) x [ 1 - 1.14^(-12)] <=> X = $7858.44
As one day use would save Ithaca $400, to achieve the targeted saving of $7858.44, the city has to use the snowplow at least 20 days per year ( 7858.44/400)
