studying for a test, cant figure out this probability problem
A bin at Blockbuster contains 100 DVD's of which 20 are defective. You randomly select 10 and try them out at home. You discover that there 2 defective DVD's in the 10 that you selected. The store now allows you to select 2 replacements from the same bin (which now only has 90 DVD's in it, since you already removed 10). What is the probability that none of 10 DVD's you finally end up with are defective? What is the answer to this question if you find k defectives in your initial choice?