A quantitative data set has been grouped by using limit grouping with equal-width classes of width 5.

Question:

A quantitative data set has been grouped by using limit grouping with equal-width classes of width 5. The class limits are whole numbers.
a. If the class mark of the first class is 8, what are its lower and upper limits?
b. What is the class mark of the second class?
c. What are the lower and upper limits of the third class?
d. Which class would contain an observation of 28?