a Question 4: [8 Marks] You are faced with a decision on an investment proposal. Specifically, the estimated additional income from the investment is $180,000 per year; the initial investment costs are $640,000; and the estimated annual costs are $14,000, which begin decreasing by $4,000 per year starting at the end of the second year. Assume an 8- year analysis period, no salvage value, and MARR = 15%. (a) What is the IRR of this proposal? Is it a profitable investment? (Use i = 20% 6 an initial guess) (b) What are the simple and compounded payback periods at i = MARRP