13. Given cash flows for an investment proposal: Years 1/ $4,000, 2/ $3,600; 3/ $3,000; 4/ $2,400; and 5/$2,000. If the investment's cost is $9,000, the payback period (rounded to nearest tenth) is: a 3 years b. 4 years c. 2.5 years d. 2.9 years 2