On a statistics test students were asked to construct a frequency distribution of the blood creatine levels (units/liter) for a sample of 300 healthy subjects. The mean was 95, and the standard deviation was 40. The following class interval widths were used by the students:

(a) 1

(d) 15

(b) 5

(e) 20

(c) 10

(f) 25 Comment on the appropriateness of these choices of widths.