An investment project has annual cash inflows of $4,200,$5,100,$6,300, and $5,500, for the next four years, respectively. The discount rate is 15 percent. a. What is the discounted payback period for these cash flows if the initial cost is $6,900 ? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g., 32.16.) b. What is the discounted payback period for these cash flows if the initial cost is $9,000 ? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g. 32.16.) c. What is the discounted payback period for these cash flows if the initial cost is $12,000 ? (Do not round intermediate calculations and round your answer to 2 decimal places, e.g.,32.16.)