The answer is 204.79, if that is what you are looking for
The closest I could get was 3.1
Total number of CDs = 12
Number of CDs that can be selected at once = 2
Selecting 2 CDs from 12 means combination of 12 objects taken 2 at a time. This can be calculated by 12C2.
This means, we have 66 possible combinations to choose from