The hemoglobin A1c test, a blood test given to diabetic's patients during their periodic checkups, indicates the level of control of blood sugar during the past 2 to 3 months. The following data values were obtained for 40 different diabetics patients at a university clinic:

Classify these A1c values into a grouped frequency distribution using the classes 3.7–4.7, 4.7–5.7, and so on.
What are the class midpoints for these classes