The following are the duration in minutes of a sample of long-distance phone calls made within the continental United States reported by one long-distance carrier. Time (in Minutes) Relative Frequency 0 but less than 5 0.37 5 but less than 10 0.22 10 but less than 15 0.15 15 but less than 20 0.10 20 but less than 25 0.07 25 but less than 30 0.07 30 or more 0.02 what is the width of each class?