Four students from each of the grade levels 4 through 8 at Wilson School were selected at random andsurveyed about the number of books they read. The scatterplot above shows the number of complete independent-reading books, y, that each of the 20 students read during the last school year. A line of best fit for the data is also shown and has the equation y = 2x i 4, where x is the grade level of the student. How many more independent-reading books did Tasha read than the number of books predicted by the given line of best fit for someone in her grade?