Compute the payback period and net present value

Question

Task: The cash flow for projects A, B, C are given below:

Year    ProjectA    ProjectB    ProjectC
0          -1000        -1000        -1000
1              0           1000            0
2           2000            0              0
3          -1000         1000         3000

1) Calculate the payback period and net present value for each project (assuming a 10% discount rate).

2) If A and B are mutually exclusive and C is independent, which project, or combination of projects, is preferred using (1) the payback method or (2) the net present value method? What does the result tell you about the value-additivity properties of the payback method?