Retsac Company is considering an investment of $20,000 in an automated teaching robot. Retsac's cost of capital is 6%. Retsac anticipates the following net cash inflows from the teaching robot:

Year 1$5,000

Year 2$8,000

Year 3$14,000

Year 4$14,000

• Calculate the cash payback period for the teaching robot. Show your work.
• Calculate the net present value for the teaching robot. Use the appropriate table. Show your work.
• Calculate the profitability index for the teaching robot. Show your work.
• Calculate the internal rate of return for the teaching robot. Use Excel.