An investment project costs $$10,000$ and has annual cash flows of $$2,800$ for six years.

a$.$

What is the discounted payback period if the discount rate is zero percent? $($Enter $0$ if the project never pays back. Do not round intermediate calculations and round your answer to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$

b$.$ What is the discounted payback period if the discount rate is $4$ percent? $($Enter $0$ if the project never pays back. Do not round intermediate calculations and round your answer to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$

c$.$ What is the discounted payback period if the discount rate is $21$ percent? $($Enter $0$ if the project never pays back. Do not round intermediate calculations and round your answer to $2$ decimal places, e$.$g$.,32\mathrm{.}16.)$