A music store has 90 different CD's. If an average price is $12 per CD and 20 of the most expensive ones are $20 each, what is the average price of the remaining CD's?  Choose the correct choice from the following answers.
A) 8.33  B) 8.75  C) 9.23  D) 9.71  E) 10.07
The sum of the prices of all CD's is (90 * $12 = $1,080).   The sum of the prices of the most expensive CD's is $400. So, ($1,080 - $400 = $680) is left for 70 remaining CD's. Thus the average price is (frac{$680}{70} = $9.71)
<result>D</result>
A music store has 90 different CD's. If an average price is $12 per CD and 20 of the most expensive ones are $20 each, what is the average price of the remaining CD's?