18.5 A new demonstration system has been designed by Custom Baths & Showers. For the data shown, determine the sensi- tivity of the rate of return to the amount of the revenue gradient G for values from $1500 to $2500. If the MARR is 18% per year, would this variation in the revenue gradient affect the decision to build the demonstration system? Work this prob- lem (a) by hand and (b) by computer. P = $74,000 n = 10 years S= 0) Expense: $30,000 first year, increasing $3000 per year thereafter Revenue: $63,000 first year, decreasing by G per year thereafter