A ball is made of rubber, when dropped on a concrete floor, bounces up to 80% of the height from which it was dropped. The ball is dropped from 2m. After how many bounces will the ball not rise over 0.5 m?

This is what I did

.5 = 2(.8) ^n

.25 = .8^n

ln .25 = n ln .8

n = 6.2

Now, what would be the answer 6 drops or 7 drops