100 surnames were

The class interval in the data is having varying width.

(i) We know that the area of the rectangle is proportional to the frequencies in the histogram.

The class interval with minimum class size 2 is selected and the length of the rectangle is proportional to it. The proportion of the surnames per 2 letters interval can be calculated as:

(ii) The class interval in which the maximum number of surname lie is 6-8.