Data was collected for 228 randomly selected 10-minute intervals. For each ten-minute interval, the number of people entering the atrium of a large mall were recorded. The data is summarized in the histogram below. 20 40 60 80 220 240 260 280 300 320 Number of People in 10 min Frequency [Graphs generated by this script: setBorder(54,40,20,5); initPicture(202,320,0,86);axes(1000,20,1,1000,20); fill="blue"; stroke="black";line([220,-1.72],[220,1.72]); text([220,0],"220","below");line([240,-1.72],[240,1.72]); text([240,0],"240","below");line([260,-1.72],[260,1.72]); text([260,0],"260","below");line([280,-1.72],[280,1.72]); text([280,0],"280","below");line([300,-1.72],[300,1.72]); text([300,0],"300","below");line([320,-1.72],[320,1.72]); text([320,0],"320","below");textabs([165,0],"Number of People in 10 min","above");textabs([0,115],"Frequency","right",90);rect([220,0],[240,64]);rect([240,0],[260,53]);rect([260,0],[280,8]);rect([280,0],[300,86]);rect([300,0],[320,17]);] What is the class width for this histogram (and corresponding GFDT)? Note: Each class contains its lower class limit, but not its upper class limit