I hope someone can help.

I'm trying to calculate what the instantaneous rate of change would be at year 2 for the following table:

I'm suppose to plot these points on a graphing calculator and then find the values of y (students per computer) that are close to year 2, then use these points to calculate the instantaneous rate of change. The only problem is that I don't have a graphing calculate on hand that has the power to do this. Are there any only resources that could be a close substitute? Please let me know.