I am trying to calculate an ROI for a Human Resource Information System. I need to do one over a four year period. The average cost per employee...

I am trying to calculate an ROI for a Human Resource Information System. I need to do one over a four year period. The average cost per employee would be $2 monthly; I have employees. How do I figure out the cost of implementation which would include maintenance, administration, training..etc. I have 500 employees. It wouldnt let me retype.