Member Months of Membership
1 47
2 84
3 16
4 60
5 53
6 89
7 54
8 68
9 47
10 68
11 41
12 80
13 33
14 66
15 38
16 46
17 51
18 53
19 41
20 25

what is the probability that a member has been with the ymca between 3.5 and 4 years?