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Suppose the relationship between your study time and your grade on a Economics midterm is given by the following table:

If you study for Your grade will be
4 hours 81
5 hours 88
6 hours 94

What is the "marginal grade improvement (MGI)" of the 5th hour of studying?

points

What is the "marginal grade improvement (MGI)" of the 6th hour of studying?

points

Why might the MGI be diminishing?