GoFlo is a small growing firm that is considering the purchase of another truck to serve GoFlo's expanding customer base. The new truck will cost $21,000 and should generate annual net cash flows of $6,000 over the truck's 5-year life. What is the discounted payback period for this project if the company has a cost of capital of 8%?

a) 3 years

b) 4.28 years

c) 3.3 years

d) 3.5 years