Anyone good at frequency distribution?

[Wagram]

Alright. I have spent hours it seems looking this problem over and I simply just don't get how this professor wants me to set up the class intervals.

Here's the problem:

10
12
15
16
16
17
17
23
24
25
30
31
31
31
33
35
35
36
36
38
38
38
40
40
42
43
44
45
47
47
48
52
53
55
60
61
62
63
64
64
66
69
70
73
75
79
81
81
84
85

a.) Construct a frequency distribution using five class intervals

b.) Construct a frequency distribution using ten class intervals.

Ok here is my problem. I understand that the range is 10 - 85. So the class width would be 75/5 = 15. They make us use some term "under" in the class intervals. So I had this but I doubt it is correct.

Class Intervals	Frequency
10 - 25	10
26 - 40	14
41 - 55	10
56 - 70	9
71 - 85	7