The following cash flows are given for a project

C0 = -9000 C1= +9000 C2= +18000

The NPV of the project at a discount rate of 50% is:

A.) 18,000 B.) 5,000 C.) 11,000 D.) zero or E.) none of these

The IRR for this project is:

A.) 10% B.) 25% C.) 50% D.) 100% or E.) none of these

The payback period for this project is:

A.) zero years B.) one year C.) two years D.) three years or E.) none of these.

So Im pretty sure the NPV is B.) 5,000 and the IRR is D.) 100% but I cannot figure out the payback period can someone please help.