A northwestern distribution company surveyed 53 of its midlevel managers. The survey obtained the ages of these managers, which later were organized into the frequency distribution shown. Determine the class midpoint, relative frequency, and cumulative frequency for these data.
Class Interval Frequency
20–under 25 ............. 8
25–under 30 ............. 6
30–under 35 ............. 5
35–under 40 ............. 12
40–under 45 ............. 15
45–under 50 ............. 7