The following are the number of undergraduate units earned by 40 salesmen of certain company. 48 60 96 78 120 54 72 72 102 108 96 110 52 60 66 120 42 60 112 65 85 54 125 84 90 66 48 83 84 96 79 86 93 110 120 86 99 88 73 88 Construct a frequency distribution with 7 classes. Use 42 as the lowest lower-class limits.